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Elsevier Editorial System(tm) for The Journal of Supercritical fluids Manuscript Draft Manuscript Number: SUPFLU-D-12-00163R2 Title: High-pressure liquid-liquid equilibrium boundaries for systems containing polybutadiene and/or polyethylene and a light solvent or solvent mixture Article Type: Regular Paper Keywords: Polybutadiene; Polyethylene; Dimethyl ether; n-Pentane; Cloud point; Liquid-liquid equilibrium Corresponding Author: Dr. Marcelo Santiago Zabaloy, PhD Corresponding Author's Institution: Universidad Nacional del Sur - Planta Piloto de Ingeniería Química -CONICET First Author: Juan M Milanesio, Ph D Order of Authors: Juan M Milanesio, Ph D; Guillermo D Mabe, Bachelor in Chemical Engineering; Andrés E Ciolino, Ph D; Lidia M Quinzani, Ph D; Marcelo Santiago Zabaloy, PhD Abstract: In this work, we have obtained experimental cloud points, i.e., liquid-liquid equilibrium boundaries at constant composition, for the systems 'polybutadiene (PB) + n-pentane (C5)', 'PB + dimethyl ether (DME) + C5', 'polyethylene (PE) + DME + C5', and 'PB + PE + DME + C5'. The temperature range of the experiments was from 50 to 184 °C. The maximum pressure was 303 bar. In all cases the overall polymer concentration was less than or equal to 4.1 wt%. At the ranges of conditions of the experiments we have found the following: (a) For PB + C5, the minimum pressure required to guarantee homogeneity is 140 bar. (b) For 'PB + C5 + DME', the cloud point pressure (CPP) curves lie in between the CPP curves of 'PB + DME' and 'PB + C5', and the maximum CPP was 226 bar. The CPP increases with the increase of the DME/C5 ratio in the solvent mixture. (c) For 'PE + DME + C5', there is a substantial decrease in the CPPs with the addition of C5 to the DME + C5 solvent mixture, and the maximum CPP was 303 bar. (d) The CPPs for 'PB + PE + DME + C5' are higher than the CPPs of 'PB + DME + C5' but lower than the CPPs of 'PE + DME + C5'.
October 23rd 2012
Ms. Ref. No.: SUPFLU-D-12-00163R1
Dear Richard,
In response to your e-mail, which I reproduce below, I inform you that we have
made all the required editorial corrections, and have uploaded the corresponding
files.
Among the files uploaded yesterday, we have not replaced the one
corresponding to the Supplementary Material, which did not require changes.
The problems in the “References” section seems to arise during the production
of the PDF file by the EES web site. Please Check the source file, i.e., the file
“MiMaCiQuiZa REV paper corr UNLINKED.doc”, which should show all the
references with their complete bibliographic information.
Best Regards.
Dr Marcelo S. Zabaloy Profesor Adjunto – Investigador Independiente Universidad Nacional del Sur - Planta Piloto de Ingenieria Quimica PLAPIQUI (UNS-CONICET) Camino La Carrindanga Km 7 Casilla de Correo 717 (8000) Bahia Blanca ARGENTINA Phone: 54-291-486-1700 Ext. 232 FAX : 54-291-486-1600 e-mail: mzabaloy@plapiqui.edu.ar
Cover Letter
Your Submission martes, 23 de octubre de 2012, 7:55
De:
"Richard Smith" <smith@scf.che.tohoku.ac.jp> Agregar remitente a Contactos
Para: mzabaloy@plapiqui.edu.ar
Cc: smith@scf.che.tohoku.ac.jp
Ms. Ref. No.: SUPFLU-D-12-00163R1
Title: High-pressure liquid-liquid equilibrium boundaries
for systems containing polybutadiene and/or polyethylene and
a light solvent or solvent mixture
The Journal of Supercritical Fluids
Dear Marcelo,
I have studied the revisions made to the text and am very
satisfied with the changes made by the authors. However,
there are a number of editorial corrections (attached pdf
file) that I hope that you can make at your earliest
convenience. Please note that many of these changes are
small. However, some may require some checking due to some
missing numbers in the reference section that may be due to
only formatting.
After I receive the next revision, I will be able to issue a
formal acceptance letter. Please note that while all files
will need to be resubmitted, responses to the reviewers are
not needed or a reply to this letter can be used instead if
the EES system requires the file.
To submit a revision, please go
to http://ees.elsevier.com/supflu/ and login as an Author.
Your username is: mszabaloy
If you need to retrieve password details, please go to:
http://ees.elsevier.com/supflu/automail_query.asp
On your Main Menu page is a folder entitled "Submissions
Needing Revision". You will find your submission record
there.
Yours sincerely,
Richard L. Smith
Note: a “Response to Reviewers” file is not required, according to the e-mail
reproduced below, which includes the following paragraph:
“After I receive the next revision, I will be able to issue a
formal acceptance letter. Please note that while all files
will need to be resubmitted, responses to the reviewers
are not needed or a reply to this letter can be used instead if the EES system requires the file.”
Your Submission martes, 23 de octubre de 2012, 7:55
De:
"Richard Smith" <smith@scf.che.tohoku.ac.jp> Agregar remitente a Contactos
Para: mzabaloy@plapiqui.edu.ar
Cc:
smith@scf.che.tohoku.ac.jp
Ms. Ref. No.: SUPFLU-D-12-00163R1
Title: High-pressure liquid-liquid equilibrium boundaries
for systems containing polybutadiene and/or polyethylene and
a light solvent or solvent mixture
The Journal of Supercritical Fluids
Dear Marcelo,
I have studied the revisions made to the text and am very
satisfied with the changes made by the authors. However,
there are a number of editorial corrections (attached pdf
file) that I hope that you can make at your earliest
convenience. Please note that many of these changes are
small. However, some may require some checking due to some
missing numbers in the reference section that may be due to
only formatting.
After I receive the next revision, I will be able to issue a
formal acceptance letter. Please note that while all files
will need to be resubmitted, responses to the reviewers are
not needed or a reply to this letter can be used instead if
the EES system requires the file.
To submit a revision, please go
to http://ees.elsevier.com/supflu/ and login as an Author.
*Response to Reviewers
Your username is: mszabaloy
If you need to retrieve password details, please go to:
http://ees.elsevier.com/supflu/automail_query.asp
On your Main Menu page is a folder entitled "Submissions
Needing Revision". You will find your submission record
there.
Yours sincerely,
Richard L. Smith
Receiving Editor
The Journal of Supercritical Fluids
1
High-pressure liquid-liquid equilibrium boundaries for systems containing
polybutadiene and/or polyethylene and a light solvent or solvent mixture
Juan M. Milanesio, Guillermo D. B. Mabe, Andrés E. Ciolino, Lidia M. Quinzani and Marcelo S. Zabaloy
PLAPIQUI – Planta Piloto de Ingeniería Química, Universidad Nacional del Sur - CONICET, Cno. La Carrindanga km. 7, CC 717 – 8000 – Bahía Blanca, Argentina
Corresponding author. Tel 0054 (0291-4861700 ext 232). E-mail: mzabaloy@plapiqui.edu.ar
*Graphical Abstract (for review)
1
High-pressure liquid-liquid equilibrium boundaries
for systems containing polybutadiene and/or polyethylene and a
light solvent or solvent mixture
Juan M. Milanesio, Guillermo D. B. Mabe, Andrés E. Ciolino, Lidia M. Quinzani and
Marcelo S. Zabaloy
PLAPIQUI – Planta Piloto de Ingeniería Química, Universidad Nacional del Sur - CONICET, Cno. La
Carrindanga km. 7, CC 717 – 8000 – Bahía Blanca, Argentina
Cloud point pressure (CPP) of the system ‘polybutadiene (PB) + n-pentane (C5)
+ dimethyl ether (DME)’ increases with an increase in DME/C5 ratio.
CPP of the system ‘polyethylene (PE) + DME + C5’ substantially decreases with
addition of C5 to the DME + C5 solvent mixture.
CPPs for ‘PB + PE + DME + C5’ are higher than the CPPs of ‘PB + DME + C5’ but
lower than the CPPs of ‘PE + DME + C5’.
Corresponding author. Tel 0054 (0291-4861700 ext 232). E-mail: mzabaloy@plapiqui.edu.ar
*Highlights (for review)
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1
High-pressure liquid-liquid equilibrium boundaries
for systems containing polybutadiene and/or polyethylene
and a light solvent or solvent mixture
Juan M. Milanesio, Guillermo D. B. Mabe, Andrés E. Ciolino, Lidia M. Quinzani
and Marcelo S. Zabaloy
PLAPIQUI – Planta Piloto de Ingeniería Química, Universidad Nacional del Sur - CONICET,
Cno. La Carrindanga km. 7, CC 717 – 8000 – Bahía Blanca, Argentina
Abstract
In this work, we have obtained experimental cloud points, i.e., liquid-liquid equilibrium
boundaries at constant composition, for the systems 'polybutadiene (PB) + n-pentane
(C5)', „PB + dimethyl ether (DME) + C5', 'polyethylene (PE) + DME + C5', and 'PB +
PE + DME + C5'. The temperature range of the experiments was from 50 to 184 °C.
The maximum pressure was 303 bar. In all cases the overall polymer concentration
was less than or equal to 4.1 wt%. At the ranges of conditions of the experiments we
have found the following: (a) For PB + C5, the minimum pressure required to
guarantee homogeneity is 140 bar. (b) For „PB + C5 + DME‟, the cloud point pressure
(CPP) curves lie in between the CPP curves of „PB + DME‟ and „PB + C5‟, and the
maximum CPP was 226 bar. The CPP increases with the increase of the DME/C5
ratio in the solvent mixture. (c) For „PE + DME + C5‟, there is a substantial decrease
Corresponding author. Tel 0054 (0291-4861700 ext 232). E-mail: mzabaloy@plapiqui.edu.ar
*ManuscriptClick here to view linked References
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2
in the CPPs with the addition of C5 to the DME + C5 solvent mixture, and the
maximum CPP was 303 bar. (d) The CPPs for „PB + PE + DME + C5‟ are higher than
the CPPs of „PB + DME + C5‟ but lower than the CPPs of „PE + DME + C5‟.
Keywords: Polybutadiene, Polyethylene, Dimethyl ether, n-Pentane, Cloud point, Liquid-
liquid equilibrium
1. Introduction
Supercritical fluids can be used in chemical reactions as solvents and also as reactive
components [1]. Examples of such reactions are oxidative reactions in supercritical water,
the high pressure polymerization of ethylene to produce polyethylene, and the production of
methyl-ethyl-ketone using supercritical butene [1]. In particular, hydrogenation reactions
performed using supercritical or near-critical solvents display higher reaction rates than the
conventional hydrogenation reaction. For example, the hydrogenation of sunflower oil using a
platinum catalyst, and supercritical propane as solvent, can be up to twelve times faster than
the conventional process [2]. Bertucco et al. [3] have reported an increase in the reaction
rate for the hydrogenation of unsaturated ketones, in the presence of supercritical CO2. Van
den Hark et al. [4] also reached extremely high reaction rates in the hydrogenation of fatty
acid methyl esters to obtain fatty alcohols, using supercritical propane as the solvent. The
important advantage of using a solvent at supercritical conditions is that the hydrogenation
process occurs in a homogeneous (fluid) medium, whereas, in the conventional
hydrogenation process, the system has always, at least, two fluid phases during the reaction
progress. The mass transfer resistance in the first case is much smaller than in the
conventional hydrogenation.
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3
In the particular case of polybutadiene (PB), the complete hydrogenation yields a copolymer
of ethylene and 1-butene (hPB) which highly resembles the structure of linear low-density
(LLD) polyethylene (PE) (LLDPE). Furthermore, PB may be synthesized using the anionic
polymerization technique, that makes possible to obtain polymers of very narrow molecular
weight distribution (Mw/Mn < ~1.2). Consequently, the hydrogenation of PBs obtained by
anionic polymerization can produce LLDPEs of narrow molecular weight distribution [5-16].
Information on conventional methods for hydrogenating PB is provided as supplementary
material.
To hydrogenate the PB under supercritical conditions, the solvent (or solvent mixture) should
be able to simultaneously dissolve the PB and the hydrogen. Moreover, the solvent mixture
should also dissolve the reaction product, i.e., the hydrogenated PB (hPB), if the reaction
rate were not high enough to achieve complete PB saturation before the partially
hydrogenated polymer precipitates. The high asymmetry of the reactive mixture, which is due
to the large difference in size between the H2 and PB molecules, implies a high immiscibility
level in the absence of the supercritical solvent or solvent mixture. On the other hand, the
subsystem 'solvent mixture + H2', should be miscible at the reaction conditions. The
subsystems 'PB + solvent mixture' and „PE + solvent mixture‟ (or hPB + solvent mixture) also
present a significant level of asymmetry. The 'PB + solvent mixture' subsystem should also
be homogeneous at the conditions of temperature, pressure and PB concentration range, at
which the hydrogenation is carried out.
The knowledge of the phase behavior of the subsystems of the reaction mixture should be
useful for estimating the operating conditions of the supercritical hydrogenation reactor.
Since the composition of the reaction mixture changes with the extent of reaction, so does its
phase condition. Some of the mentioned subsystems are the following: 'unsaturated polymer
+ solvent mixture', 'saturated polymer + solvent mixture' and 'unsaturated polymer +
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4
saturated polymer + solvent mixture'. These subsystems are related to the initial, final and
intermediate stages of the hydrogenation reaction, respectively.
The presence of a co-solvent, which together with the solvent makes up a solvent mixture,
could be useful to decrease the pressure needed to have an homogeneous reactive mixture,
throughout the reaction course. If this last condition were met, then, the solvent mixture
would be able to keep the unsaturated and the partially hydrogenated polymers
simultaneously dissolved within a single phase. The effect of the co-solvent concentration, on
the phase behavior of the subsystems of the reaction mixture, should be accounted for to
estimate the operating conditions of the hydrogenation reactor. The study of the phase
behavior of subsystems related to the PB hydrogenation has to pay attention to the nature of
the saturated and partially saturated polymers, to the reaction extent, and to the nature, and
relative concentrations within the solvent mixture, of the solvent and co-solvent.
Few authors have studied the high-pressure fluid phase behavior of „polymer + light solvent‟
systems for PB, hPB or PE. Winoto et al. [17] determined cloud-point pressures (CPPs) for
„PB + supercritical propane‟ and for „hPB + supercritical propane‟ at 0.5 wt% polymer
concentration. Using n-pentane (C5) as the solvent, Yeo et al. [18] determined isothermal
phase boundaries and the critical polymer concentrations for the pseudobinary system 'PE +
C5' at two different polymer molecular weights. Zhang et al. [19] measured isoplethic liquid-
liquid phase transitions for the same pseudobinary system and also studied the effect of the
addition of carbon dioxide as a co-solvent on the CPPs. Lee et al. [20] determined
experimental cloud points for the system 'PE + dimethyl ether (DME)' at high pressure. We
use the word “pseudobinary” instead of the word “binary” to mean that at least one of the
components of the system is not monodisperse.
In a previous work, Milanesio et al. [21] experimentally found, using a variable-volume
windowed equilibrium cell, homogeneity conditions, i.e., cloud points, for the pseudobinary
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5
mixtures propane + PB, diethyl ether (DEE) + PB, DME + PB, and DEE + high-density PE. In
PB-containing pseudobinary systems, at the ranges of conditions of the experiments [21], the
minimum pressure required to guarantee homogeneity, at any temperature, was below 200
bar for DEE, below 300 bar for DME and in the order of 500 bar when using propane as
solvent. The data for „PE + DEE‟ [21] indicated the need for a minimum pressure of about
240 bar to keep the system within a single phase. Milanesio et al. [21] suggested the use of
binary solvent mixtures, i.e., a combination of two solvents, since this would make it possible
to carry out the supercritical hydrogenation of PB under fluid homogeneity conditions while
operating the supercritical reactor at relatively moderate temperature and pressure. To
dissolve the hydrogen and carry out the hydrogenation reaction, a light solvent with relatively
low critical temperature and pressure is the better choice [21]. In contrast, the dissolution of
the polymers is boosted by a minimum degree of asymmetry between the polymer and the
solvent, i.e., by heavier solvents [21]. This led to suggesting the use of solvent mixtures
made of a light solvent and a relatively heavier one [21].
In this work, we experimentally determined liquid-liquid phase boundaries (CPPs), and hence
homogeneity conditions, not covered in reference [21], for a number of subsystems related to
the potential supercritical hydrogenation of PB. Such subsystems are the following: (a) 'PB +
C5', (b) 'PB + DME + C5' , (c) 'PE + DME + C5', and (d) 'PB + PE + DME + C5'. The choice
of DME as one of the solvents is because it presents a good trade off between the required
pressure for dissolving PB (below 300 bar, [21]) and the value of is critical temperature
(127.0 °C,Table 2). Propane has a more convenient critical temperature value (96.7 °C,
[22]) but requires higher pressures for dissolving PB (in the order of 500 bar, [21]). With
regard to the heavier solvent, which together with DME makes up the solvent mixture
suggested in ref [21], we chose in this work n-pentane (C5). It is non polar, and hence has
affinity with the product of hydrogenation. Besides, it could be more miscible with PB than
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6
propane, since C5 has a higher molecular weight than propane. This last conjecture was
confirmed by the results obtained in this work.
In system (a) the solvent is a pure compound (C5), and in systems (b), (c) and (d) the solvent
is a mixture (DME + C5). System (b) is a subsystem of the initial reactive mixture, where the
polymer (PB) is unsaturated. System (c) would be representative of a subsystem of the final
reactive mixture, since the polymer (PE) is fully saturated. System (d) corresponds to an
intermediate extent of reaction where the polymer is not fully hydrogenated, and a subsystem
of the reactive mixture is made of the solvent mixture (DME + C5) and a partially
hydrogenated polymer [emulated as a mixture of fully unsaturated (PB) and fully saturated
(PE) polymers].
Notice that in the systems 'PE + DME + C5' and 'PB + PE + DME + C5', the PE is considered
as representative of the hPB. CPP values are determined in this work as a function of
temperature and overall polymer concentration by using a variable-volume windowed
equilibrium cell. This cell can be used at pressures up to 1000 bar and at temperatures up to
200 °C.
Altough this work has been motivated by the problem of hydrogenating polybutadiene in a
supercritical media, we have not yet measured cloud points for hydrogen-containing
systems, neither have we conducted supercritical hydrogenation experiments. This was also
the case in ref [21].
2. Experimental
2.1 Materials
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7
One PB and one PE are the polymers used in this work. The PB was synthesized by anionic
polymerization under a high vacuum inert atmosphere [11, 21]. The PE is a high density
commercial polyethylene from Du Pont de Nemours & Co. (USA). The number-average
molecular weight (Mn), the weight-average molecular weight (Mw), polydispersity index
(Mw/Mn) and 1,2-vinyl content of the synthesized PB is given in Table 1, as well as the
molecular properties of the PE. The equipment and conditions used to obtain the information
listed in Table 1 are described elsewhere [21].
Dimethyl ether (DME), with a purity level greater than 99% (GC), was purchased from
Sigma-Aldrich (St. Louis, Missouri, USA). Laboratorios Cicarelli (San Lorenzo, Santa Fe,
Argentina) provided the n-pentane (C5) with a purity level greater than 99% (GC). Table 2
provides the values of some relevant physical properties for the solvents used in our
experiments. Table 3 reports the properties of polymers used in the literature, in papers that
are cited, for comparison purposes, in this work.
2.2 Apparatus and Procedure
We performed the experimental determination of cloud-point pressures in polymer + solvent
systems with the aid of a variable volume equilibrium cell, built on the basis of equipment
described in the literature [23-27]. The details of the apparatus have been given elsewhere
[21]. We describe here only the main features of the apparatus and of the experimental
procedure.
The experimental setup is represented in Fig. 1. The variable-volume windowed equilibrium
cell can operate at pressures up to 1000 bar and temperatures up to 200 °C. The variable-
volume nature of the cell makes it possible to control pressure and temperature
independently. The cell has a movable (free) piston. A manual pressure generator is used to
move the piston, with the help of a hydraulic fluid, so that the system pressure can be
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8
adjusted to the desired value. By using the words “variable volume cell” we mean that the
volume occupied by the sample, i.e., by the mixture of interest, is variable. A stirring magnet
is placed inside the cell. A glass window and an associated system of light-emitting-diodes
(LEDs) makes possible to visually observe the cell contents, i.e., to detect phase transitions.
A PID controller keeps the cell temperature at the desired value. The controller acts on a
couple of heating elements that surround a solid aluminum shell that tightly houses the cell.
The “cell + shell + heating elements” system is placed within an air thermostatized chamber.
The temperature of the fluid system inside the cell is measured using a J-type thermocouple.
The uncertainty in the reported temperature values is estimated to be in the order of ±1 °C.
The pressure of the fluid mixture under study is measured using a certified absolute pressure
transducer (Paroscientific Inc., Model 430K-101, range: 0 to 30.000 psi, accuracy ±0.02% of
reading). The estimated uncertainty in the cloud-point pressure values reported in this work
is about 3 bar.
The experimental procedure is the following. To load the cell, a known amount of polymer, or
mixture of polymers of known polymer/polymer ratio, (weighed to ±0.01 g on a precision
scale BP 410 Sartorius balance) is placed on a small slightly concave piece of glass. Such
glass tray is introduced into the cell, and the cell is closed and placed inside the air
thermostat chamber. The glass tray is used as a polymer loading device and as a dissolution
surface. The solvent (either DME, or C5, or a DME+C5 mixture of known DME/C5 mass
ratio) is loaded into the cell by using an auxiliary cell. The mass of solvent introduced into the
main cell is determined by weighing the auxiliary cell before and after loading the solvent. At
the end of the loading process the cell contains a „polymer/s + solvent/s‟ mixture of known
composition. Next, the system is set under conditions of temperature and pressure such that
a homogenous fluid is seen through the cell window. Then, the pressure is slowly reduced, at
constant temperature, by using the manual pressure generator, until the fluid system
becomes opalescent. The opalescence appearance conditions correspond to the cloud point,
at which a new incipient dense phase arises. When the system was taken back to higher
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9
pressures, to repeat the cloud point determination, a reproducibility of ±3 bar was obtained in
most cases.
3. Results
This section reports the experimental cloud point pressures obtained in this work for a
number of systems. The uncertainties in reported weight fraction values were estimated
through a very conservative propagation of error analysis, for all systems studied in this
work.
3.1. Pseudobinary system PB16 + C5
Raw experimental data (cloud points) for the system 'PB16 + C5' at three different overall
polymer weight fractions: 1.1 0.1, 3.3 0.3 and 3.6 0.4 wt% are reported in Table 4. The
temperature range of the data is from 111 to 184 °C and the pressure range is from 19 to 134
bar. All data correspond to temperatures which are subcritical with respect to that of the
pure solvent (196.7 °C, Table 2). Fig. 2 shows the CPP data (Table 4) obtained in this work as
a function of temperature for this system. At a set overall composition, the homogeneous
region lies above the cloud point experimental data. The dashed lines in Fig. 2 and following
figures correspond to smoothed data and they have been added to facilitate the visualization
of the trends set by the experimental data. Fig. 2 shows the following: (a) a pressure of about
140 bar should be enough to completely dissolve the PB16 in C5, (b) the PB16 overall
concentration influences the behavior of the cloud-point pressure, and (c) the CPP of the
'PB16 + C5' system does not have a monotonical behavior with composition, i.e., the 3.3 PB16
wt% mixture presents the largest values of CPPs within the temperature range of Fig. 2. Item
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10
(a) confirms the expectation that C5 could be more miscible with PB than propane, which
requires pressures in the order of 500 bar for full miscibility with PB [21]. We ascribe the
higher miscibility of PB in C5 to the higher molecular weight of C5.
3.2. Pseudoternary systems
For the pseudoternary system 'PB16 + DME + C5', we obtained the experimental CPPs at
two different overall polymer weight fractions, i.e., at 4.1 ± 0.4 PB16 wt% and at 2.6 ± 0.2
PB16 wt%. The temperature and pressure ranges for the data are from 50 °C to 179 °C and
from 30 bar to 226 bar respectively. Table 5 presents the raw experimental data measured in
this work for this system, and the CPPs values are shown in Fig. 3 (see “x” and “+” markers).
These two isoplethic series differ not only in the overall polymer weight fraction, but also in
the DME/C5 ratio in the solvent mixture. For the isopleth of 4.1 ± 0.4 PB wt% we used a
solvent mixture with 30 wt% of C5 and 70 wt% of DME. For the isopleth of 2.6 ± 0.2 PB wt%
we used a solvent mixture with 67 wt% of C5 and 33 wt% of DME.
Figure 3 also shows two additional data sets. One of them corresponds to PB16 + DME [21]
and the other to PB16 + C5 (Table 4). This last data set has already been shown in Fig. 2.
Due to the varying polymer concentration in Fig. 3, it is not possible to reach definitive
enough conclusions on the effect of the composition of the solvent mixture on the cloud point
pressure. However, the information provided in Fig. 3 supports the following conjectures: (a)
at constant temperature, the CPP increases with the increase in the DME concentration in
the solvent mixture, and (b) at constant pressure the cloud point temperature (CPT)
increases with the increase of the C5 concentration in the solvent mixture. The solubility of
PB16 in a solvent is expected to increase both, with the polarity and with the molecular
weight of the solvent. DME is more polar than C5 (see the dipole moment values in Table 2),
but it has a lower molecular weight than C5 (Table 2). Therefore, when going from DME to
C5, as solvents for PB16, two opposite effects compete: the decrease in the solvent polarity
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11
and the increase in the solvent molecular weight. Fig. 3 shows that the second effect is
stronger than the first.
For the pseudoternary system 'PE53 + DME + C5', we obtained the CPPs for two different
isopleths with the following overall polymer weight fractions: 2.9 ± 0.3 PE53 wt% and 2.7 ±
0.3 PE53 wt%. The solvent mixture for the first isopleth had 78 wt% of C5 and 22 wt% of
DME, and for the second one it had 53 wt% of C5 and 47 wt% of DME. The raw
experimental data measured in this work for this system are presented on Table 6. The
temperature range for the experimental data is from 115 °C to 176 °C. The pressure range is
from 147 bar to 303 bar. Figure 4 shows the CPPs of Table 6 together with two additional
CPP series from the literature (systems 'PE + DME' and PE + C5', [19-20]). The
pseudobinary data were included to discuss the effect of the solvent mixture on the phase
boundaries. It is important to note that different isopleths have different overall polymer
concentrations in Fig. 4. Besides, we stress that different polyethylenes (PE28, PE53 and
PE65) are considered in Fig. 4. Despite such differences, Fig. 4 suggests the following
conjecture: the addition of DME to the solvent mixture shifts the cloud point curve towards
higher pressures. Notice that DME is a polar co-solvent (Table 2). The solubility of PE is
expected to be higher for non polar solvents, an to increase with the increase in the solvent
molecular weight. When going from DME to C5, as in Fig. 4, the polarity of the solvent
decreases and, simultaneously, the molecular weight of the solvent increases. Both changes
promote the increase in the PE solubility. That is what we observe in Fig. 4.
3.3. Pseudoquaternary system PB16 + PE53 + DME + C5
The system 'PB16 + PE53 + DME + C5' is related to the hydrogenation reaction of PB16 that
would be carried out using a DME + C5 mixture as reaction media. The presence of the two
polymers and of the solvent mixture emulates a subsystem that could be found at
intermediate extents of reaction. The raw CPP experimental data for this system are
presented in Table 7. The composition of the mixture was 1.2 ± 0.1 PE53 wt% and 2.1 ± 0.2
1 2 3 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 61 62 63 64 65
12
PB16 wt% in a solvent mixture made of 42 wt% of DME and 58 wt% of C5. The experimental
data were obtained at temperatures from 134 to 177 °C and pressures from 234 to 292 bar.
Fig. 5 shows the experimental results for the pseudoquaternary system 'PB16 + PE53 +
DME + C5' ( “x” markers). The CPPs for the pseudoquaternary system are located in
between the CPPs measured in this work for the pseudoternary systems 'PB16 + DME + C5'
and 'PE53 + DME + C5'. The three series of experimental data shown in Fig. 5 have a similar
overall polymer concentration. But the composition of the solvent mixture for 'PB16 + DME +
C5' (filled circles) differs significantly from that for the systems 'PB16 + PE53 + DME + C5' (
“x” markers) and 'PE53 + DME + C5' (empty circles). However, from our previous results
shown in Fig. 3, which consider the effect of the solvent mixture composition on the location
of „PB + DME + C5‟ isopleths, there should be no qualitative change in the relative positions
of the different cloud point curves in Fig. 5, if the 'PB16 + DME + C5' system had a solvent
mixture composition comparable to that of the other systems. Because of such expectation,
we have added to Fig. 5 a line of cloud-points predicted for a system made of 2.6 PB16 wt%
in a 50/50 wt% DME/C5 solvent mixture (dotted line). It was obtained by interpolating our
pseudoternary raw experimental data displayed in Fig. 3, which have a variable solvent
mixture composition. The predicted cloud points show more clearly that the behavior of the
pseudoquaternary system is in between those of the corresponding pseudoternary systems,
under the conditions of our experiments.
The supplementary material provides additional information on the significance of
experimental data from the literature related to this work.
4. Remarks and conclusions
In this work we experimentally found, using a variable-volume windowed equilibrium cell,
homogeneity conditions, i.e., cloud point pressures (CPPs) at given temperature and overall
1 2 3 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 61 62 63 64 65
13
composition, for the systems C5 + PB, 'PB + DME + C5', „ PE + DME + C5' and 'PB + PE +
DME + C5'. This new information should be helpful in the process of identifying proper
conditions for carrying out the supercritical hydrogenation of PB. In all cases the overall
polymer concentration was less than or equal to 4.1 wt%. The temperature range for the
experiments done in this work goes from 50 to 184 °C. The maximum pressure measured is
303 bar.
The maximum temperature for the „PB + C5‟ experiments is below (but fairly close to) the
critical temperature of C5 (Table 4). For PB + C5, at the ranges of conditions of the
experiments (111 to 184 °C, 1.1 to 3.6 PB wt%), the minimum pressure required to
guarantee homogeneity is about 140 bar (Fig. 2, Table 4). For „PB + C5 + DME‟, the CPP
curves (Table 5) were found to be located in between the CPP curves of the corresponding
pseudobinary systems „PB + DME‟ and „PB + C5‟ (Fig. 3). The maximum CPP obtained for
this system is 226 bar (at 156 °C). The CPP at a given temperature increases with the
increase in the DME/C5 ratio in the solvent mixture (Fig. 3).
For „PE + DME + C5‟ we observe a substantial decrease in the CPPs, mainly at low
temperatures, with the addition of C5 to the DME + C5‟ solvent mixture (Fig. 4). The
maximum CPP, measured in this work, for this pseudoternary system was 303 bar (at 176
°C, Table 6).
To emulate a subsystem of the reactive mixture at an intermediate reaction extent in a
potential PB hydrogenation progress, we measured the phase boundary (CPPs) of the
pseudoquaternary system „PB + PE + DME + C5‟ (Table 7, Fig. 5) . The solvent mixture has
a solvent ratio close to 1:1 (DME/C5, weight basis). The CPP values for this system are
higher than the CPPs obtained for the pseudoternary system „PB + DME + C5‟ but lower
than the CPPs for the saturated polymer (PE) in the same solvent mixture.
1 2 3 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 61 62 63 64 65
14
The experimental data obtained in this work make it possible to partially establish the effect
of the nature of the polymer (saturated, unsaturated), of the composition of the solvent
mixture, and of the reaction extent, on the liquid-liquid phase boundaries of a number of
subsystems of the reaction mixture in the potential hydrogenation of PB in supercritical
media. From considering “PB hydrogenation”-related experimental data, from this work and
from the literature, it seems that the use of a solvent mixture constituted by a lighter, e.g.,
DME, and a heavier, e.g., C5, solvent is a convenient choice to carry out the single-fluid-
phase supercritical hydrogenation of PB at relatively moderate conditions. These
observations should be confirmed in the future through phase equilibrium experiments on
“PB hydrogenation”-related hydrogen-containing mixtures and also by performing actual
hydrogenation experiments.
The experimental data obtained in this work could be useful to develop models of the
equation of state (EOS) type. The accurate reproduction of the complex phase behavior of
the highly asymmetric systems here studied would be a stringent test for such models.
5. Acknowledgements
We gratefully acknowledge the financial support of the Argentinean institutions:
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad
Nacional del Sur (UNS), and Agencia Nacional de Promoción Científica y
Tecnológica (ANPCyT). We also wish to thank, for their valuable contributions, to Dr.
Angel Satti (PLAPIQUI/UNS), Dr. Horacio Thomas (CINDECA/UNLP) and Dr.
Cristian Vitale (INIQO/UNS). We are also grateful to Prof. Esteban A. Brignole and to
Dr. Pablo E. Hegel (PLAPIQUI/UNS) for helpful discussions.
6. Supplementary Material
1 2 3 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 61 62 63 64 65
15
Additional information related to this work is available as supplementary material.
1 2 3 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 61 62 63 64 65
16
Table 1. Characteristics of polymers used in this work
Polymer Acronym Mw / (g/mol) Mn / (g/mol) PD Index* 1,2-Vinyl content / %
Polybutadiene PB16 16600 15800 1.05 15
Polyethylene
(HDPE)
PE53 53000 22000 2.4 -
* PD = Mw / Mn
1 2 3 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 61 62 63 64 65
17
Table 2: Properties of Pure Solvents [22]
Compound M / (g/mol) Tc / °C Pc / bar C m
n-pentane (C5) 72.2 196.7 33.6 0
dimethyl ether (DME) 46.1 127.0 53.7 4.34 10-30
M = Molecular weight, Tc =critical temperature, Pc =critical pressure, = dipole moment. The
unit C m corresponds to “coulomb times meter”
1 2 3 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 61 62 63 64 65
18
Table 3. Polymers from the literature cited in this work
Polymer Acronym Mw / (g/mol) Mn / (g/mol) PD Index* Reference
polyethylene
polyethylene
PE65
PE28
64800
27700
52100
13900
1.2
2.0
[20]
[19]
* PD = Mw / Mn
1 2 3 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 61 62 63 64 65
19
Table 4. Experimental Cloud Points for the pseudobinary system
polybutadiene (PB) + n-pentane (C5) (This work)
1.1 PB16 wt% 3.3 PB16 wt% 3.6 PB16 wt%
T / °C P / bar T / °C P / bar T / °C P / bar
123 19 111 26 118 25
127 28 116 35 126 39
133 36 122 44 138 55
136 43 125 50 146 68
141 48 128 55 155 79
145 53 132 63 165 94
149 62 138 72 174 108
154 69 144 82 183 117
158 72 147 87
165 77 152 93
168 83 158 101
173 89 163 109
178 96 170 118
174 122
178 126
184 134
1 2 3 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 61 62 63 64 65
20
Table 5. Experimental Cloud Points for the pseudoternary
system polybutadiene (PB) + n-pentane (C5) + dimethyl ether
(DME) (this work)
4.1 PB16 wt%
Solvent: 70/30 wt% (DME/C5)
2.6 PB16 wt%
Solvent: 33/67 wt% (DME/C5)
T / °C P / bar T / °C P / bar
50 30 96 48
59 47 106 66
69 73 117 87
79 92 127 104
88 100 137 118
98 119 148 136
107 142 158 148
117 160 168 161
127 179 179 174
136 195
147 210
156 226
1 2 3 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 61 62 63 64 65
21
Table 6. Experimental Cloud Points for the pseudoternary
system polyethylene (PE) + n-pentane (C5) + dimethyl ether
(DME) (this work)
2.7 PE53 wt%
Solvent: (47/53) wt% (DME/C5)
2.9 PE53 wt%
Solvent: (22/78) wt% (DME/C5)
T / °C P / bar T / °C P / bar
115 253 116 147
131 265 123 154
137 269 129 160
142 274 134 167
147 279 140 174
152 282 141 177
158 288 147 183
162 292 152 190
167 296 157 195
171 298
176 303
1 2 3 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 61 62 63 64 65
22
Table 7. Experimental Cloud Points for the pseudoquaternary
system polybutadiene (PB) + polyethylene (PE) + n-pentane
(C5) + dimethyl ether (DME) (this work).
1.2 PE53 wt% and 2.1 PB16 wt%
Solvent: (42/58) wt% (DME/C5)
T / °C P / bar
134 234
136 239
139 244
146 251
152 246
155 259
160 272
163 276
168 288
172 287
177 292
1 2 3 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 61 62 63 64 65
23
List f Figure Captions
Figure 1. Experimental setup. 1. Equilibrium cell, 2. Air thermostat, 3. Glass Window, 4. Stirring magnet, 5.
Piston, 6. Polymer loading tray, 7. Aluminum shell. PT: Pressure Transducer, TS: Temperature sensor, PG:
manual Pressure Generator, TC: Temperature controllers, SMD: Stirring magnet driver.
Figure 2. Experimental cloud-point pressure as a function of temperature for the system 'PB16 + C5' at three
different overall polymer weight fractions (This work). Rhombuses: 1.1 PB16 wt%. Triangles: 3.3 PB16 wt%.
Squares: 3.6 PB16 wt%. Rhombuses, triangles and squares: raw experimental data (this work). Dashed lines:
smoothed data. Solid line: liquid-vapor saturation line for pure C5 [22]. Star: C5 critical point [22] (Table 2). For
molecular properties of PB16 see Table 1.
Figure 3. Experimental cloud-point pressure as a function of temperature for the systems 'PB16 + DME', 'PB16 +
C5 + DME' and 'PB16 + C5' at four different overall polymer weight fractions. Markers: Empty squares: 4.6 PB16
wt% in pure DME (raw experimental data from [21]). “X”: 4.1 PB16 wt% in a solvent mixture of (70/30) wt% of
(DME/C5) (This work). “+”: 2.6 PB16 wt% in a solvent mixture of (33/67) wt% of (DME/C5) (This work). Filled
squares: 3.6 PB16 wt% in pure C5 (This work). Dashed lines: smoothed data. For molecular properties of PB16
see Table 1.
Figure 4. Experimental cloud-point pressure as a function of temperature for the systems 'PE65 + DME', 'PE53 +
C5 + DME' and 'PE28 + C5' at four different overall polymer weight fractions. Markers: Empty circles: 5.0 PE65
wt% in pure DME (raw experimental data from [20]). ”+”: 2.7 PE53 wt% in a solvent mixture of (47/53) wt% of
(DME/C5) (This work). “X”: 2.4 PE53 wt% in a solvent mixture of (22/78) wt% of (DME/C5) (This work). Filled
circles: 2.0 PE28 wt% in pure C5 (raw experimental data from [19]). Dashed lines: smoothed data. For molecular
properties of PE53, PE65 and PE28 see Tables 1 and 3
Figure 5. Cloud-point pressure as a function of temperature for the pseudoternary systems „PB16 + C5 + DME‟,
„PE53 + C5 + DME‟ and for the pseudoquaternary system „PB16 + PE53 + C5 + DME‟ at three different overall
polymer weight fractions and with different solvent mixtures. Markers: Experimental data from this work. Empty
circles: 2.7 PE53 wt% in a solvent mixture of (47/53) wt% (DME/C5) (This work). “X”: 1.2 PE53 wt% and 2.1 PB16
wt% in a solvent mixture of (42/58) wt% (DME/C5) (This work). Filled circles: 2.6 PB16 wt% in a solvent mixture of
1 2 3 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 61 62 63 64 65
24
(33/67) wt% of (DME/C5) (This work). Dashed lines: smoothed data. Dotted line: predicted cloud-point pressure
as a function of temperature for 2.6 PB16 wt% in (50/50) wt% (DME/C5). The dotted line was obtained by
interpolating raw experimental data shown in Fig. 3. For molecular properties of PE53 and PB16 see Table 1.
1 2 3 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 61 62 63 64 65
25
Figure 1. Experimental setup. 1. Equilibrium cell, 2. Air thermostat, 3. Glass Window, 4. Stirring magnet, 5.
Piston, 6. Polymer loading tray, 7. Aluminum shell. PT: Pressure Transducer, TS: Temperature sensor, PG:
manual Pressure Generator, TC: Temperature controllers, SMD: Stirring magnet driver.
1 2 3 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 61 62 63 64 65
26
Figure 2. Experimental cloud-point pressure as a function of temperature for the system 'PB16 + C5' at three
different overall polymer weight fractions (This work). Rhombuses: 1.1 PB16 wt%. Triangles: 3.3 PB16 wt%.
Squares: 3.6 PB16 wt%. Rhombuses, triangles and squares: raw experimental data (this work). Dashed lines:
smoothed data. Solid line: liquid-vapor saturation line for pure C5 [22]. Star: C5 critical point [22] (Table 2). For
molecular properties of PB16 see Table 1.
0
20
40
60
80
100
120
140
160
100 120 140 160 180 200
0
20
40
60
80
100
120
140
160
100 120 140 160 180 200
Pre
ss
ure
/ b
ar
Temperature / ºC
1.1 PB16 wt%
3.3 PB16 wt%
3.6 PB16 wt%
VP n-pentane
0
20
40
60
80
100
120
140
160
100 120 140 160 180 200
0
20
40
60
80
100
120
140
160
100 120 140 160 180 200
Pre
ss
ure
/ b
ar
Temperature / ºC
1.1 PB16 wt%
3.3 PB16 wt%
3.6 PB16 wt%
VP n-pentane
1 2 3 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 61 62 63 64 65
27
Figure 3. Experimental cloud-point pressure as a function of temperature for the systems 'PB16 + DME', 'PB16 +
C5 + DME' and 'PB16 + C5' at four different overall polymer weight fractions. Markers: Empty squares: 4.6 PB16
wt% in pure DME (raw experimental data from [21]). “X”: 4.1 PB16 wt% in a solvent mixture of (70/30) wt% of
(DME/C5) (This work). “+”: 2.6 PB16 wt% in a solvent mixture of (33/67) wt% of (DME/C5) (This work). Filled
squares: 3.6 PB16 wt% in pure C5 (This work). Dashed lines: smoothed data. For molecular properties of PB16
see Table 1.
0
50
100
150
200
250
300
20 40 60 80 100 120 140 160 180 200
Temperature / ºC
Pre
ss
ure
/ b
ar
0
50
100
150
200
250
300
20 40 60 80 100 120 140 160 180 200
4.6 PB16 wt% in DME
4.1 PB16 wt% in n-pentane (30%) + DME (70%)
2.6 PB16 wt% in n-pentane (67%) + DME (33%)
3.6 PB16 wt% in n-pentane
0
50
100
150
200
250
300
20 40 60 80 100 120 140 160 180 200
Temperature / ºC
Pre
ss
ure
/ b
ar
0
50
100
150
200
250
300
20 40 60 80 100 120 140 160 180 200
4.6 PB16 wt% in DME
4.1 PB16 wt% in n-pentane (30%) + DME (70%)
2.6 PB16 wt% in n-pentane (67%) + DME (33%)
3.6 PB16 wt% in n-pentane
1 2 3 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 61 62 63 64 65
28
Figure 4. Experimental cloud-point pressure as a function of temperature for the systems 'PE65 + DME', 'PE53 +
C5 + DME' and 'PE28 + C5' at four different overall polymer weight fractions. Markers: Empty circles: 5.0 PE65
wt% in pure DME (raw experimental data from [20]). ”+”: 2.7 PE53 wt% in a solvent mixture of (47/53) wt% of
(DME/C5) (This work). “X”: 2.4 PE53 wt% in a solvent mixture of (22/78) wt% of (DME/C5) (This work). Filled
circles: 2.0 PE28 wt% in pure C5 (raw experimental data from [19]). Dashed lines: smoothed data. For molecular
properties of PE53, PE65 and PE28 see Tables 1 and 3
0
200
400
600
800
1000
1200
1400
110 130 150 170 190
Temperature / ºC
Pre
ss
ure
/ b
ar
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
110 130 150 170 190
5.0 PE65 wt% in DME
2.7 PE53 wt% in n-pentane (53%) + DME (47%)
2.4 PE53 wt% in n-pentane (78%) + DME (22%)
2.0 PE28 wt% in n-pentane
0
200
400
600
800
1000
1200
1400
110 130 150 170 190
Temperature / ºC
Pre
ss
ure
/ b
ar
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
110 130 150 170 190
5.0 PE65 wt% in DME
2.7 PE53 wt% in n-pentane (53%) + DME (47%)
2.4 PE53 wt% in n-pentane (78%) + DME (22%)
2.0 PE28 wt% in n-pentane
1 2 3 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 61 62 63 64 65
29
Figure 5. Cloud-point pressure as a function of temperature for the pseudoternary systems „PB16 + C5 + DME‟,
„PE53 + C5 + DME‟ and for the pseudoquaternary system „PB16 + PE53 + C5 + DME‟ at three different overall
polymer weight fractions and with different solvent mixtures. Markers: Experimental data from this work. Empty
circles: 2.7 PE53 wt% in a solvent mixture of (47/53) wt% (DME/C5) (This work). “X”: 1.2 PE53 wt% and 2.1 PB16
wt% in a solvent mixture of (42/58) wt% (DME/C5) (This work). Filled circles: 2.6 PB16 wt% in a solvent mixture of
(33/67) wt% of (DME/C5) (This work). Dashed lines: smoothed data. Dotted line: predicted cloud-point pressure
as a function of temperature for 2.6 PB16 wt% in (50/50) wt% (DME/C5). The dotted line was obtained by
interpolating raw experimental data shown in Fig. 3. For molecular properties of PE53 and PB16 see Table 1.
1 2 3 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 61 62 63 64 65
30
6. References
[1] G. Brunner, Applications of Supercritical Fluids, Annual Review of Chemical and
Biomolecular Engineering, 1 (2010) 321-342.
[2] C.M. Piqueras, G. Tonetto, S. Bottini, D.E. Damiani, Sunflower oil hydrogenation on Pt
catalysts: Comparison between conventional process and homogeneous phase operation using
supercritical propane, Catalysis Today, 133-135 (2008) 836-841.
[3] A. Bertucco, P. Canu, L. Devetta, A.G. Zwahlen, Catalytic Hydrogenation in Supercritical
CO2: Kinetic Measurements in a Gradientless Internal-Recycle Reactor, Ind Eng Chem Res,
36 (1997) 2626-2633.
[4] S. van den Hark, M. Härröd, Hydrogenation of oleochemicals at supercritical single-phase
conditions: influence of hydrogen and substrate concentrations on the process, Appl Catal A-
Gen, 210 (2001) 207-215.
, O. Curzio, C. S , Model linear
ethylene-butene copolymers irradiated with γ-rays, Polymer, 40 (1999) 3443-3450.
[6] J.M. Carella, W.W. Graessley, L.J. Fetters, Effects of chain microstructure on the
viscoelastic properties of linear polymer melts: Polybutadienes and hydrogenated
polybutadienes, Macromolecules, 17 (1984) 2775-2786.
, L.M. Quinzani, Structure of partially hydrogenated
polybutadienes, Polymer, 39 (1998) 5573-5577.
[8] Y. Doi, A. Yano, K. Soga, D.R. Burfield, Hydrogenation of polybutadienes.
Microstructure and thermal properties of hydrogenated polybutadienes, Macromolecules, 19
(1986) 2409-2412.
[9] H.G.M. Edwards, D.W. Farwell, A.F. Johnson, I.R. Lewis, N.J. Ward, N. Webb,
Spectroscopic studies of an ambient-pressure process for the selective hydrogenation of
polybutadienes, Macromolecules, 25 (1992) 525-529.
[10] D.J. Lohse, S.T. Milner, L.J. Fetters, M. Xenidou, N. Hadjichristidis, R.A. Mendelson,
C.A. García-Franco, M.K. Lyon, Well-Defined, Model Long Chain Branched Polyethylene. 2.
Melt Rheological Behavior, Macromolecules, 35 (2002) 3066-3075.
[11] M. Morton, Anionic Polymerization: Principles And Practice, Academic Press, Nueva
York, 1983.
[12] J.S. Parent, N.T. McManus, G.L. Rempel, RhCl(PPh3)3 and RhH(PPh3)4 Catalyzed
Hydrogenation of Acrylonitrile-Butadiene Copolymers, Ind Eng Chem Res, 35 (1996) 4417-
4423.
[13] D.S. Pearson, L.J. Fetters, W.W. Graessley, G. Ver Strate, E. Von Meerwall, Viscosity
and self-diffusion coefficient of hydrogenated polybutadiene, Macromolecules, 27 (1994)
711-719.
[14] J. Perez, Estructura y Propiedades de Copolímeros Modelo de Etileno Modificados
Químicamente. PhD Thesis, in, Universidad Nacional del Sur, Bahía Blanca, 2003.
[15] H. Rachapudy, G.G. Smith, V.R. Raju, W.W. Graessley, Properties of Amorphous and
Crystallization Hydrocarbon Polymers - 3. Studies of the Hydrogenation of Polybutadiene, J
Polym Sci Polym Phys Ed, 17 (1979) 1211-1222.
[16] P.V.C. Rao, V.K. Upadhyay, S. Muthukumaru Pillai, Hydrogenation of polybutadienes
catalyzed by RuCl2(PPh3)3 and a structural study, Europ Polym J, 37 (2001) 1159-1164.
[17] W. Winoto, M. Radosz, K. Hong, J.W. Mays, Amorphous polystyrene-block-
polybutadiene and crystallizable polystyrene-block-(hydrogenated polybutadiene) solutions in
compressible near critical propane and propylene - Hydrogenation effects, J Non-Cryst Solids,
355 (2009) 1393-1399.
1 2 3 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 61 62 63 64 65
31
[18] S.-D. Yeo, I.-S. Kang, E. Kiran, Critical Polymer Concentrations of Polyethylene
Solutions in Pentane, Journal of Chemical & Engineering Data, 47 (2002) 571-574.
[19] W. Zhang, C. Dindar, Z. Bayraktar, E. Kiran, Phase behavior, density, and crystallization
of polyethylene in n-pentane and in n-pentane/CO2 at high pressures, Journal of Applied
Polymer Science, 89 (2003) 2201-2209.
[20] S.H. Lee, M.A. LoStracco, B.M. Hasch, M.A. McHugh, Solubility of poly(ethylene-co-
acrylic acid) in low molecular weight hydrocarbons and dimethyl ether. Effect of copolymer
concentration, solvent quality, and copolymer molecular weight, J Phys Chem, 98 (1994)
4055-4060.
[21] J.M. Milanesio, G.D.B. Mabe, A.E. Ciolino, L.M. Quinzani, M.S. Zabaloy, Experimental
cloud points for polybutadiene + light solvent and polyethylene + light solvent systems at
high pressure, The Journal of Supercritical Fluids, 55 (2010) 363-372.
[22] DIPPR, Evaluated Process Design Data., Thermophysical Properties Laboratory. Design
Institute for Physical Property Data, BYU-DIPPR. American Institute of Chemical
Engineers., Provo, Utah, 2003.
[23] S.J. Chen, R.E. Randelman, R.L. Seldomridge, M. Radosz, Mass spectrometer
composition probe for batch cell studies of supercritical fluid phase equilibria, J Chem Eng
Data, 38 (1993) 211-216.
[24] T.W. de Loos, W. Poot, G.A.M. Diepen, Fluid phase equilibria in the system
polyethylene + ethylene. 1. Systems of linear polyethylene + ethylene at high pressure,
Macromolecules, 16 (1983) 111-117.
[25] C.J. Gregg, F.P. Stein, C.K. Morgan, M. Radosz, A variable-volume optical pressure-
volume-temperature cell for high-pressure cloud points, densities, and infrared spectra,
applicable to supercritical fluid solutions of polymers up to 2 kbar, J Chem Eng Data, 39
(1994) 219-224.
[26] M.A. McHugh, T.L. Guckes, Separating polymer solutions with supercritical fluids,
Macromolecules, 18 (1985) 674-680.
[27] V.J. Oliveira, C. Dariva, J.C. Pinto, High-pressure phase equilibria for polypropylene-
hydrocarbon systems, Ind Eng Chem Res, 39 (2000) 4627-4633.
Supplementary MaterialClick here to download Supplementary Material: MiMaCiQuiZa REV paper SUPPL MAT UNLINKED.pdf