Reference Viscosities of H2, CH4, Ar, And Xe at Low Densities
DENSITIES, ELEC'TRICAL CONDUCTIVITIES, VISCOSITIES AND ... · densities, elec'trical...
Transcript of DENSITIES, ELEC'TRICAL CONDUCTIVITIES, VISCOSITIES AND ... · densities, elec'trical...
FRANK J. SELLER RESEARCH LABORATORY
FJSRL-TR-82-0006
JULY 1982
DENSITIES, ELEC'TRICAL CONDUCTIVITIES,
VISCOSITIES AND PHASE EQUILIBRIA OF
1,3-DIALKYLIMIDAZOLIUM CHLORIDE -
ALUMINUM CHLORIDE BINARY AND
TERNARY MELTS
ARMAND A. FANNIN, DANILO A. FLOREANI,
LOWELL A. KING, JOHN S. LANDERS,
BERNARD J. PIERSMA, DANIEL J. STECH A
ROBERT L. VAUGHN, JOHN S. WILKES,
JOHN L. WILLIAMS
PROJECT 2303
40 •AIR FORCE SYSTEMS COMMAND
UNITED STATES AIR FORCE
MDT1ON STAbt M Un.i it0 8_ ufmstrlbuuv iUrajnited
Sr ..- r-. .-- •, .• ? ,• •- " ;• "- r- rv .¶ -- - . .... .- . ... V - - .. . • •
FJSRL-TR-82-0006
This document was preparea by the Electrochemistry Division, Directorateof Chemical Sciences, Frank J. Seiler Research Laboratory, United States AirForce Academy, CO. The research was conducted under Project Work Unit number2303-F2-10. Lowell A. King was the project scientist.
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Lowell A.Kine Ariand A. Fannin, Jr, Lt CoProject Scientist Director, Chemical Sciences
WIliam D. Siuru) Jr., Colonel
Commander
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I. REPORT NUMBER 12. GOVT ACCESSION NO. 3. RECIPfENT'S CATALOG NUMBER
FJSRL-TR-82-0006 , lADA.I/ ,.9 . E
4, TITLE (ad Subtitle) 5. TYPE OF REPORT & PERIOD COVERED
Densities, Electrical Conductivities,Viscosities and Phase Equilibria of 1,3- Interim 6/81-7/82Dialkylimidazolium Chloride-Aluminum Chloride 6. PERFORMING ORG. REPORT NUMBERBinary and Ternary Melts
7. AUTHOR(&) Armand A. Fannin, Jr., DaniloTT".Floreaeini, 8. CONTRACT OR GRANT NUMBER(s)
Lowell A. King*, John S. Landers, Bernard J.Piersma, Daniel J. Stech, Robert L. Vaughn, JohnS. Wilkes, John L. Williams
9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK
The Frank J. Seiler Research Laboratory (AFSC) AREA & WORK UNIT NUMBERS
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The Frank J. Seiler Research Laboratory (AFSC) July 1982FJSRL/NC 13. NUvMSEAoF PAGESUSAF Academy, CO 80840 38
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molten salt.densityconductivityviscosity
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'1%. ABSTRACT (Coqtinue n reveree side If necessary and Identify by block number)
/.xperimental values are reported of the specific electrical conductivities,densities and kinematic viscosities of representative examples of binary 1,3-dialkylimidazolium chloride-aluminum chloride mixtures. The electrical con-ductivities of ternary mixtures of 1-methyl-3-ethylimidazolium chloride, al-uminum chloride, and several organic and inorganic third components also arereported. All of these data were collected over wide temperature and com-position ranges. The phase diagram for the l-methyl-3-ethylimidazolium chlo-ride-aluminum chloride system was determined.
IFORM
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SECURITY- CLASSIFICATION OF THIS PAGE (When Data Entered)
FJSRL-TR-82-0006
DENSITIES, ELECTRICAL CONDUCTIVITIES, VISCOSITIESAND PHASE EQUILIBRIA OF 1,3-DIALKYLIMIDAZOLIUM CHLORIDE-
ALUMINUM CHLORIDE BINARY AND TERNARY MELTS
Lt Col Armand A. Fannin, Jr.2Lt Danilo A. Floreani
Dr. Louell A. KingMaj John S. Landers
Dr. Bernard J. Piersma2Lt Daniel J. Stech
Maj Robert L. VaughnDr. John S. Wilkes
Capt John L. Williams
JULY 1982Approved for public release; distribution unlimited.
Directorate of Chemical SciencesThe Frank J. Seiler Research Laboratory
Air Force Systems CommandU. S. Air Force Academy, Colorado 80840
II
TABLE OF CONTENTS
S lUMMARY i*i
PREFACE. . . . . . . . . . ............ ii.
INTRODUCTION . . . . . . . . . . . ..
-EXPERIMENTAL . . . .. .. .. .... ... .... 2
RESULTS AND DISCUSSION ................ ...... 7
REFERENCES . . . . . . . . . . . . . . . . . . . . 34
• iI
AcceSCAOfl ForNTIS Gr P•&tDTIC Tt3B
I;IDistributilol/
• j ~Availabilitt Codles
.Avail j nd/or l
i
SUMMARY
1'
* - Experimental values are reported of the specific electrical conductiv-
ities, densities and kinematic visccsities of representative examples of
binary 1,3-dialkylimidazolium chloride-aluminum chloride mixtures. The elec-
trical conductivities of ternary mixtures of l-iethyl-3-ethylimidazolium
chloride, aluminum chloride, and several organic and inorganic third compon-
ents also are reported. All of these data were collected over wide temper-
ature and composition ranges. The phase diagram for the 1-methyl-3-ethyl-
imidazolium chloride-aluminum chloride system was determined.
I II
I'I
4 ii
PREFACE "
Many binary compositions of 1,3-dialkylimidazolium chloride and aluminum
chloride are ionic liquids which are liquid near (and in some cases well
below) room temperature. They are potentially useful as electrolytes in bat-
teries, for electroplating, and in photoelectrochemical cells. They have also
been used as solvents in the investigation of a number of organic, organo-
metallic, and inorganic solutes. The work described here is part of a con-
tinuing study designed to develop new low temperature electrolytes for battery
applications. Experimental work is continuing, and theoretical modeling of
the results is in progress. More complete results and their interpretation
will be reported at a later date.
Dr. King gratefully acknowledges the financial support of the Air ForceI -I"Wright Aeronautical Laboratories. Dr. Piersma gratefully acknowledges his
support by the Air Force Office of Scientific Research as a University Res-
ident Research Professor at the Frank J. Seiler Laboratory. Maj Landers par-
ticipated in the project as a USAF Academy Faculty Research Associate. Lts
Floreani, Stech and Wilson contributed to this effort while on temporary duty
with the Frank J. Seiler Laboratory, awaiting Air Force assignment.
iii
INTRODUCTION
Molten salts have been considered as potential primary and secondary bat-
tery electrolytes for several years. As part of ongoing programs at the Frank
J. Seiler Research Laboratory and the Air Force Aero-Propulsion Laboratory, we
report here the specific electrical conductivities, densities, and kinematic
viscosities of several bi'Jary mixtures of 1,3-dialkylimidazolium chloride and
aluminum chloride over wide temperature and composition ranges. We also
report the specific conductivities of certain l-methyl-3-ethylimidazolium
chloride (MeEtImCl)-aluminum chloride binaries to which several organic and
inorganic compounds have been individually added. We have determined the
phase diagram for the MeEtImCl-AlC1 3 binary system over most of the poss-
ible composition range.
One other major class of room temperature molten salts has been studied as
a potential battery electrolyte and for other applications; that is the
1-alkylpyridinium chloride-aluminum chloride system. Extensive work has been
done on this system in various laboratories. Studies in room temperature
aluminum halide-containing melts in general were the subject of a recent
review by Chum and Osteryoung (1). The present study parallels our early work
on the densities, conductivities, and viscositiec of the alkylpyridinium
systems (2).
The dialkylimidazolium chlorides used in this study are shown below:
Compound Ri R9
MeMeImCl methyl methylcv+ NR C- MeEtlmCl methyl ethyl
MePruImCfl methyl n-propyl
MeBuImCil methyl n-butylBuBuInCl _n-butyl n-butyl
1
The rationale for the choice of these imidazolium salts has been discussed.,
elsewhere as has their synthesis and the preparation of the binary melts
(4,5).
The third components which were added to the dialkyl imidazolium chloride-K
aluminum chloride binaries were acetonitrile, propionitrile, butyronitrile,
benzene, xylene, and lithium chloride.
EXPERIMENTALF Sample preparation.- The dialkylimidazolium salts and their binary mix-
tures with AlCl, were prepared as described elsewhere, (4,5). Ternary mix-
4 tures were prepared by adding redistilled reagent grade third components to
previously prepared binary melts (except for LiCl, which first was dried by
prolonged heating just below its melting point). All sample preparation and
handling (except in sealed dilatometers and viscometers) was conducted in a
argon filled glove box (Vacuum/Atmospheres Company box and Model MO-40 DRI
TRAIN), having moisture and oxygen concentrations less than 10 ppm.
Density measurements.- Densities were measured in sealed Pyrex dilato-
metric tubes whose volumes had been calibrated with mercury or distilled water
in the conventional manner. Etched on each dilatometer was a reference mark
midway up the stem (6). Samples which could be handled conveniently as
liquids (except for the MeEtImCl binaries) were loaded into dilatometers with
bulbs on the bottom of a relatively small diameter stem. The volume of this
type of dilatometer to the reference mark was typically 6.5 cm', and that of
the stem typically 0,085 cm'/cm. The remaining samples were loaded into
straight tubes of typical volumes and cross sections of 1.5 cm' and 0.24
cm'/cm, respectively.
2
Weighings were made inside the glove box. Loaded dilatomneters were stop-
.pered, removed from the glove box, evacuated, and sealed with a torch. The
dilatometers were placed in a B. Braun Thermomix Model 1420 water bath, and
temperatures monitored with an Air Force Standard Platinum Reference Thermo-
meter. Estimated uncertainty in sample temperature was ±0.05 *C. At temp-
eratures below 20 0C and above 85 0C, the dilatometers were placed in the con-
stant temperature bath described below in the viscosity section. The experi-
mental measurements of sample volumes were made by measuring with a cathe-
tometer the distance of the bottom of the meniscus from the reference mark.
Cathetometer readings of the index mark Pand meniscus locations were made to an
accuracy of ±0.05 mm. Appropriate corrections were made in calibration and
sample measurements for bouyancy, thermal expansion, and meniscus shape
effects. Overall precision in density was estimated to be ±0.1% and ±1%
for samples in the large and small dilatometers, respectively.
Conductivity measurements.- The same conductance cell was used for all
samples, and is shown in Fig. 1. It was a Pyrex capillary approximately 0.5
cm long with a nominal i.d. of 0.05 cm. The capillary wi.s sealed to a 0.6 cm
i.d. Pyrex tube. Bright platinum wire coils were placed inside the larger
Pyrex tube, immediately above the capillary, aud on the outside surface of the
capillary. A thermocouple was also inserted into the larger Pyrex tube. The
assembly was immersed to approximately the same depth in small containers of
each sample. Before each filling the cell was carefully cleaned by washing
with acetonitrile and water and was dried in a 100 *C oven.
The conductance cell was calibrated at 25 'C using 0.1 demal aqueous KCI
(7). The cell constant was 214.93 cm , and was corrected for thermal
expansion as appropriate for each individual experimental measurement.
Conductivity measurements were made at 1 kllz with a Beckmani Model RGLS8A
conductivity bridge. Measurements at 1 kHz and 3 kHz were identical within
exp~rimental error, so no frequency corrections were considered necessary.
The sample containers were loaded and the conductance measurements made in
the glove box. The containers were immersed in a well stirred lninerai oil
bath to a depth where the surface of the sample was at least 5 cm below the
surface of the oil, in order to minimize temperature gradients within the
sample. Temperature stability of at least ±0.05 'C was attained over the
entire temperature range, and the actual temperatures were known to within
±0.1 *C. A Bayley Model 124 proportional temperature controller was used.
overall precision in specific conductivity was estimated to be ±1%.
Viscosity measurements,- A closed, submersible, all Pyrex viscometer
was employed, anid is shown in Fig. 2. The viscometer could be opened for
emptying, cleaning, and refilling, then resealed. The viscometer was calib- Irated at various temperatures with cyclohexanol, ethylene glycol, and glyc-er-
ol. Flow times for calibration varied between 19 and 4550 s. The calibration
data were fit to a straight line passing through the origin of a time-
*kinematic viscosity plot. The average deviation of calibration data from the
* line was ±1%.
The viscometer was mounted on a vertical platform submerged in a well
stirred silicone oil bath, The platform could be rotated in the vertical
plane by remote control to fill the upper. chamber of the viscometer. The
passage of the liquid meniscus past two arrow marks above the capillary was
timed with a precision of better than ±1.5% with a. stop watch. At least six
* runs were made for each sample at each temperature, and the mean efflux times
were used in the calculation of kinematic viscosity.
4
S.•= . , i •,• • ••• .• ,. - • .I . .. . . . . - ..•• •_ " • • • • .-. .--.------ ,• , • • '.
9 CM
2 CM
10.5 CM
12 CM
Fig. 1. Conductivity cell. Fig. 2. Viscometer.
The oil bath was equipped with submerged heaters, but the principal temp-
Lrature control was achieved with submerged coils attached to a NESLAB Endocal
Model RTE-9B refrigerated circulating bath. The oil bath could be maintained
at temperatures ranging from -15 0C to 100 'C with a long term stability of
±0.5 *C. The actual sample temperatures were known to within ±0.1 'C at
near ambient temperatures and ±0.5 'C at the temperature extremes. On com-
bining the above uncertainties with those in composition and misalignment of
4 the capillary from the vertical, an overall error in kinematic viscosity of
±2.5% was estimated.
Melting nnd freezing point measurements.- The solid-liquid phase tran-
sitions, and in some case, glass transitions were measured by two methods;
visually and by differential scanning calorimetry (DSC). Since most tran-
5
- * -c rIr. ., . mr. -.- -•**r•*r" P 9W W - - r1W . *
sitions were at sub-ambient temperatures, a conventional melting point appar-
atus could not be used for the visual determinations. A temperature con-
trolled dewar (Wilmad WG-821 variable temperature insert, WG-836 transfer
dewar, and WG-838 heater) designed for an electron paramagnetic resonance
(epr) cavity proved to be convenient for measurements to -1000 C. Samples
were sealed in quartz epr tubes and their temperature was controlled by a
stream of dry N2 gas cooled by a glass coil inmiersed in liquid N2 .
The phase transitions were observed with a magnifying glass chrough the double
quartz walls of the dewar. Many of the samples supercooled, so melting
points, rather than freezing points, were taken as the true transition temper-
ature. Glass transitions were clearly distinguished by an increase in viscos-
ity with cooling, terminated by a sudden fracturing of the melt at the glass
transition temperature.
The differential scanning calorimetry was done on a Perkin-Elmer DSC-2
calorimeter fitted with the sub-ambient accessories. Temperatures below 30 'C
were attained using liquid nitrogen cooling with a helium purge of the DSC
head. The instrument was calibrated with acetone and with water before and
after each set of experiments. The samples were contained in stainless steel
large-volume pans which were loaded and sealed inside a glove box. The temp-
erature was scanned at 10 or 20 0 C/min.
Most compositions were observed both visually and by DSC. The two methods
usually agreed within less than ±1 0C, with an estimated "worst case" error
of ±2 *C.
6
( RESULTS AND DISCUSSION
The concentrations of binary melts are expressed as the "apparent mole
fraction" of AICd 3 . This is the melt composition calculated as though the
melt were comprised of monomeric AlCl3 and the appropriate imidazolium
chloride. In fact, however, probably no measureable AlCl3 exists in these
melts (8); they are comprised of imidazolium cations and Cl, AIC 1 4,
and A1 2 CI 7 anions. The molecular weight of the binary melts is
given by
M = M + 133.34 x N 0(1-N) (1)
where M is the molecular weight of the dialkylimidazolium chloride and N is
the apparent mole fraction of AIC1 3 . Notice that this is not the custom-
ary formula for the evaluation of the molecular weight of a binary molten salt
mixture; rather it allows for the fact that the number of ions present in the
4 mixture is governed solely by the number of moles of imidazolium chloride
present, and is not changed by the addition of AIC1s (9).
Concentrations of species in ternary melts are expressed as though a third
4 component were added to an existing binary melt (which, in fact, is how they
were prepared). Aluminum chloride concentration is expressed as the apparent
mole fraction in the original binary, as defined above. The mole fraction of
4 the third component, X3 , was calculated from
X3= moles third / (moles third + moles binary) (2)
7
1. - . -
where the moles of binary can be calculated from its mass and eq. 1. Here
again, the third component does not contribute to the production of ionic
species. In the case of added LiCl, the third component does contribute ionic
species, and this method of expressing concentrations is no longer suitable
for making comparisons. (The actual mole fraction of LiCI in the one ternary
melt studied was 0.052, whereas eq. 2 would have yielded the value 0.15.)
The raw experimental data were converted into densities, specific conduc-
tivities and kinematic viscosities, and are presented for the binary melts in
Tables I, II, and III, respectively. Included in Tables I and II are the
densities and conductivities of the pure 1,3-dialkylimidazolium chlorides.
The viscosities of the pure salts and of the two lower AlClI content
binaries with MeMeImCl were not measured because of the experimental diffi-
culties which were anticipated in working with these relatively high melting
compounds in the present viscometer. It was not possible to work at an appar-
ent mole fraction AlCI 3 higher than 0.666, for the melting temperature
rose extremely rapidly with increasing AIC13 content in this composition
region. Pure aluminum chloride is a non-electrolyte, and its physical pro-
perties are not considered here.
The specific conductivities of the ternary melts to which propionitrile
has been added are given in TLble IV. Densities and viscosities of the
ternary mixtures have not been measured.
The MeEtImCl-AIC 1 3 system was chosen as a "base-line" melt, primarily
because of its relatively favorable conductivity and viscosity behavior and
its wide liquid range, as shown below. Other studies are underway in our lab-
orat-;y on nuclear magnetic resonance spectroscopy of this system and on the
electrochemical behavior of a number of inorganic and organic solutes in
MeEtImCl-AICI 3 melts.
8
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fu a- a. a0 0 wwwNO-m 0 r4O0flWr4 0 U)-4Wfli fl I-41 w o w r a: wW W a: .4Df-MMW a: WwQo(D f fxi Ia r-CmGnw a. r4LwtDWW a. tGvWW m 4
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15
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180
ft- V *T :q-4 00 (D N* 00i~ ONr C: r Y rw r 4 % rrý'~~ %Dnt; r-** 0 (n ~ %D I
v41 C;n(-tcn w O -4 ONwoý -4 r n-%D w nNDm n%0 wI CN c'
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00NO O 00
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$4 C
"04r N 00 v-NCOC- M In 00\'.NCO0OON00 0 0nIflCoO- fl" 4N 0m
1 Hi C Q n- o in f. . .*
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0n -A 0 MWr-Go I 0 d n ,! a N 6N M w't Ln M W0\N4NOCr-4 0 rN1* -4N a*\-. QuC zC 9( ý1ý0 ;;C (;, OO N IN O 04'
-H0 C4'nC It) 0r 0 C NtnO n-, 0nn% 0v-.# ýt LnD0ONN m mr0\ .
144 1: v4 -4
0 0
'r4.~
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2 v-4In zJ00 N %0D'-40c) ON4 In r- I'$ 4e0 nMr- ý0r . -.
4 r-I INI n N- Ný cn ON. i'4. 0 N N)0' WtN cI) vI N1 C- 0c) %D r-. It'. %T
0 I 0 o)%.-týt - c- N%'. 'D-4 - WN~ . o 'Tr 4Ncja In NO' 0040Z (n ( 40 00 O4-I o 000 0000
44 0 . in * . * If ON * * m *4 *C)0r IC4 CI, 4 ,-v.N CIt V.C NC I*CIn' N0 P It'I
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I- v-4 III II II ý 0c)ý rlrl n r- 0U)r
In 1.4 ,. .a 1to. ICIC
H~~ I 4Izi. 0 C v-Cv-1' I I ~ ~ I ICO '0
19
0
(0
41J
0
40 C: N4I 40 O qC, 0- I ' )U o0
C,4 -4 C4 4y) -1.o 'Jl L
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C; Cý ( (ý r:
I C1 \Q-C C r ,CH .oýo~ 'o ~ ~ r O0co A 0 0 ~
20
The freezing, melting, and glass transition data for MeEtImCl-AlCI 3
"binaries are shown in Table V.
Table V. Solid-Liquid Phase TransitionTemperatures for MeEtImCl-AlCI 3..
K T N T N T
0.00 84 0.36 -68 8.56 -18O.0S ?2 0.38 -72 0.58 -230.10 62 0.40 -7S 0.60 -310.15 S4 0.41 -27 0.61 -330.20 Al 0.42 -24 0.62 -950.25 39 0.44 -19 e.64 -950.30 32 0.46 -10 0.66 -96e.31 28 0.48 -3 0.68 450.32 21 0.50 7 0.70 790.33 19 0.S2 -3 0.73 1100.34 17 0.s4 -9 1.00 195
a Temperatures in *C.
The solid-liquid phase diagram for MeEtImCl-AlCl 3 binary melts is
shown in Fig. 3. Qualitatively, the phase equilibria are similar to those
reported by Hurley and Weir for !-ethylpyridinium bromide - aluminum chloride
binaries (10). They are not qualitatively similar to the chemically similiar
system NaCl-AICl,, as is evident from Fig. 3. All of the melting tran-
sitions are lower than for any previously reported chloroaluminate melts. In
two regions the temperatures for the transitions abruptly became lower, then
abruptly rose again. The transitions in these low temperature regions were
glass transitions, and all attempts to induce true freezing for these compo-
sitions were fruitless. The glass transitions were clearly identified by DSC
(slope change rather than a peak) and visually (fracturing of -he melts rather
than solid formation). The melting points for mixtures having aluminum chlor-
ide mole fractions greater than 0.666 were done in sealed tubes and presumably
under significant AIM. vapor pressure. No measurements were made on com-
positions greater than a mole fraction aluminum chloride of 0.73.
21
NaCI-AlC13
CD,
L 200
SMeEtImCI-AICI3
I-
0.0 0.2 0.4 0.6 0.8 1.0MOLE FRACTION AICI 3
Fig. 3. Phase diagram for MeEtImCl-AlCI 3.
Experimental densities were least squares fitted to equations of the form
P = P0 + P, (t - 60) (3)
where t is the temperature in 'C. The values of the fitted parameters are
given in Table VI, together with the valid temperature range for each compos-
ition. No unusual features were found in the densities. As expected, there
was a relatively smooth density decrease as the size of the imidazolium cation
increased. This is illustrated in Fig. 4 for N = 0.50 melts at 60 °C; similar
behavior was noted at other compositions and temperatures.
22
Table VI. Least Squares Fitted Parameters for BinaryMelt Densities.a
R1 R3 N P0 pX10x Tmin Tmax
METHYL ETHYL 0.00 1.1378 -7.8253 31 91METHYL ETHYL 0.31 1.1955 -6.0420 -20 tooMETHYL ETHYL 0.36 1.2151 -6.8975 -20 100METHYL ETHYL 0.42 1.2244 -6.3662 -20 100METHYL ETHYL 0.48 1.2531 -7.0695 0 100METHYL ETHYL 0.51 1.2667 -7.6121 0 10tMETHYL ETHYL 0.56 1.2933 -8.9639 -11 100METHYL ETHYL 0.61 1.3205 -8.5937 -20 100METHYL ETHYL 0.66 1.3498 -9.0610 -20 100METHYL METHYL 0.00 1.1745 -5.5647 127 151METHYL METHYL 0.33 1.2739 -7.5142 60 152METHYL METHYL 0.50 1.3053 -6.7460 59 152METHYL METHYL 0.66 1.3725 -9.1391 11 83METHYL PROPYL 0.00 1.0918 -7.3377 11 83METHYL PROPYL 0.33 1.1734 -6.9507 11 81METHYL PROPYL 0.50 1.2348 -7.8879 11 81METHYL PROPYL 0.66 1.3198 -8.9647 11 81METHYL BUTYL 0.00 1.0965 -6.0315 11 83METHYL BUTYL 0.33 1.1590 -4.1182 11 82METHYL BUTYL 0.50 1.2113 -7.6234 11 81METHYL BUTYL 0.66 1.303.0 -8.8205 11 82BUTYL BUTYL 0.00 1.0085 -6.7284 28 93
BUTYL BUTYL 0.33 1.0841 -6.5641 11 82BUTYL BUTYL 0.50 1.1391 -7.1948 11 82BUTYL BUTYL 0.66 1.2237 -8.1797 11 82
Temperatures in 0C; densities in g/cm
•MeMe1.30- - e TEMPERATURE 600C
,_ MOLE FRACTION AIC13= 0.50
CO MeEt:1.25 - S "•1ePr
1.20
w
1.15I I ! I IB u
2 3 4 5 5 7 8NUMBER OF ALKYL GROUP CARBONS
Fig. 4. Dependence of density on imidazolium cation size.
23
The composition dependence of the density of MeEtImCl-AlC] 3 melts at
60 0C is shown in Fig. 5. Density appears to be a monotonic function Af
AlCl3 content. Similar behavior was observed for other temperatures. For
MeEtImCl-AICI3 melts the density at each experimental composition lid
temperature was obtained by least squares fitting the methyl-ethyl billary
densities in Table I (excluding pure MeEt~mCl) to the equation
= a 0 + a, (N - 0.5) + a 2 (N - 0.5)2
+ a, (t - 60) + a, (t - 60) (N - 0.5) (4)
where the fitted values of the coefficients are a 0 1.26229, a,
0.456947, a 2 0.602142, as -7.67027 X 10- and alt
-8.97573 X 10 4.
1.35- I I I
TEMPERATURE :60%O
CI)
2 1.30 MeEtImCI-AICI 30
1.25
I.-Iz 1.20
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7MOLE FRACTION ACI 3
Fig. 5. Dependence of density on MeEtImCl-AlCl 3 melt
composition.
24
. . . . .. . - . .. . . . . . .. .- -. .-.-. .- -.. . . . . . .. . . .--. . . . . . . . .- . . . . . .. . . . + -_•. . . . • . . • . . . .
We assumed the dependence of density upon AlC13 content would be
similarly monotonic for the other four dialkylimidazolium chloride - AlCi,
systems, and therefore measured densities only at AICls mole fractions
0.00, 0.33, 0.50, and 0.66.
Experimental specific conductivities were least squares fitted to equa-
tions of the form
K= + K' (t- 60) + K 2 (t -60)2 (5)
The values of the fitted parameters are giveýn in Table VII, together with the
valid temperature range for each composition.
The dependence of specific conductivity on composition and temperature was
not as simple as for density. The dependence on cation molecular weight was
not as regular as for densities. A typical representation of this behavior
can be seen in Fig. 6, where the conductivity of equimolar MeEtImCl-AlClI
is nearly as high as that of the corresponding dimethyl salt binary, and very
substantially higher than that of the methyl-propyl analog. Similar behavior
was noted at other temperatures and compositions, as shown in Figs. 7 and 8.
These latter two figures clearly show that the specific conductivity is mark-
edly dependent upon composition of the melt, with equimolar melts being the
best conductors. The dibutyl system appears to be an exception to this at low
temperatures, where the AICl3 rich melt is the better conductor. In the
basic composition region, the relative decrease in conductivity for imidazol-
ium rich compositions becomes greater at lower temperatures, as can be seen by
comparing Figs. 7 and 8. (Missing data on these figures correspond to samples
below their melting points.)
The effects of temperature and melt composition on the equivalent conduc-
tivity of MeEtImCl-AlCls melts are shown on Fig. 9.
25
Table VII. Least Squares Fitted Parameters for BinaryMelt Specific Conductivities.2
R1 R3 N Koxle1 K1 xIe K2 xIe0 Tmin TmaxMETHYL ETHYL 0.00 0.5485 3.0871 6.4687 s2 110METHYL ETHYL 0.30 1.0401 3.648? 3.3282 36 58METHYL ETHYL 0.33 1.2276 4.0044 3,186 21 104METHYL ETHYL 0.34 1.3301 4.1150 3.4135 R2 100METHYL ETHYL 0.36 1.5267 1.4399 3.3888 8e leeMETHYL ETHYL 0.40 2.0239 5.0962 3.349? 16 85METHYL ETHYL 0.44 2.7631 S.7S40 2.5818 31 leeMETHYL ETHYL 0.48 3.8661 6.7385 2.5829 19 56METHYL ETHYL 0.49 4.1523 6.7567 2.1262 17 teoMETHYL ETHYL 0.50 4.4799 7.0092 1.9378 22 100METHYL ETHYL 0.51 4.3883 6.8528 1.?390 30 100METHYL ETHYL 0.52 4.24S4 6.6614 1.8959 18 I16METHYL ETHYL 0.58 3,6404 5.9530 2.1441 36 s8METHYL ETHYL 0.64 3,0935 4.8956 1.4423 17 100METHYL ETHYL 0.66 2.9277 4.6334 1.3388 22 104METHYL METHYL 0.00 -5.0593 15.8865 1.3204 153 164METHYL METHYL 0.33 1.4978 4.4066 4.656S 80 106METHYL METHYL 0.50 4.6324 8.4086 0.7210 80 110METHYL METHYL 0.66 3.1296 5.3115 1.?539 20 100METHYL PROPYL 0.00 0.2087 0.7552 4.8038 70 152METHYL PROPYL 0.40 1.2284 3.5281 2.7283 21 100METHYL PROPYL 0.50 2.8821 5.4980 2.1200 26 100METHYL PROPYL 0.60 2.5669 4.6650 1.6184 30 100
METHYL BUTYL 0.00 0.1231 0.1466 3.2Z60 75 110METHYL BUTYL 0.33 0.5726 2.0957 2.2568 36 100METHYL BUTYL 0.50 2.4127 4.6583 1.9272 18 100METHYL BUTYL 0.66 2.0170 3.6113 1.3517 18 100BUTYL BUTYL 0.0e 0.21S5 -0.9381 8.0692 102 11eBUTYL BUTYL 0.33 0.2268 0.88280 1.3791 6s 100BUTYL BUTYL 0.50 1.3407 2.9590 1.6109 21 100BUTYL BUTYL 0.66 1.4003 Z.6490 1.08825 18 100
Temperatures in *C; specific conductivities in ohm 1 cm 1
~0.050.05 MeMe.• ,•:•• MeEt TEMPERATURE =60*C
MOLE FRACTION AIC 3 :0.50
S~BuBu
0
I-I
RU 0.0310. 2 3 4 5 6 7 8
NUMBER OF ALKYL GROUP CARBONS
Fig. 6. Dependence of specific conductivity on imid-
azolium cation size.
26
- 0.08 TEMPERATURE-- OOC 1000
. 0.06
S0.04 MeBu
0- / BuBuo 0.02
w 0.00we----- IjI I I I IC- 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Cl)
MOLE FRACTION AIC13
Fig. 7. Dependence of specific conductivity on R1 R3 ImCl-A1C1 3- melt composition at 100 *C.
0.025 1 1TEMPERATURE- 250C
0 0.020 t -
I- 0.015-
MePr
0.010-O Me Bu0U 0.005-_o 0.005 BuBu
U-
wU 0.000 I I Ia. 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7CoMOLE FRACTION AIC13
Fig. 8. Dependence of specific conductivity on RIR3 ImCl-A1Cl 3
melt composition at 25 *C.
27
.1.
TEMPERATURE0
0.8
0.4
0.0 MelEtImCI-AICn 3
K 00.3 0.4 0.5 0.6 0.7
MOLE FRACTION AIC13
Fig. 9. Dependence of equivalent conductivity onMeEtImCl-AlCI3 melt composition and temperature.
Work is now in progress on theoretically modeling the conductivities of
these binary melts, so that the experimental results can be matched to equa-
tions derived from the transport model chosen. As was observed in
1-alkylpyridinium-AICls melts, the equivalent -onductivities did not dis-
play Arrhenius behavior very satisfactorily. This work will be reported later.
The kinematic viscosities given in Table III were converted to absolute
viscosities by
P =o (6)
The absolute viscosities of the MeEtImCl-AlCl3 melts were determined using
densities calculated from eq. 4. Kinematic viscosities of the remaining bin-
ary melts were measured at the ;ame compositions Pt which their densities were
28
determined. Therefore densities used in eq. 6 for these melts were calculated
from eq. 3.
The absolute viscosities were least squares fitted to equations of the form
loglo n 1 no + nl/T + n2/T2 (7)
where T is the temperature in kelvin. The values for the fitted parameters
are given in Table VIII, together with the valid temperature ranges for each
composition.
Table VIII. Least Squares Fitter Parameters for Binary MeltAbsolute Viscosities.a
R R N no0 ?71 X ×l) q 2 X×1O TmIn Tmix
METHYL ETHYL 0.31 7.9219 -6.1188 13.3555 10 9gMETHYL ETHYL 0.36 4.3939 -3.6006 8.7177 10 8gMETHYL ETHYL 0.46 1.7983 -1.8460 5.1768 11 98METHYL ETHYL 0.33 0.7459 -3.9566 1.7028 t2 92METHYL ETHYL 0.61 2.5833 -0.8276 5.7888 20 g8METHYL ETHYL 0.66 0.1483 -1.4269 2.1597 g 98METHYL PROPYL 0.33 8.0934 -6.2378 13.7206 11 81METHYL PROPYL e.5e 0.9359 -1.0317 3.5183 It 81METHYL PROPYL 0.66 1.5723 -1.3605 3.7797 11 $1METHYL DUTYL 0.33 4.6521 -3.9661 10.0434 20 82METHYL BUTYL e.se 2.5339 -2.e077 S.0078 2e 82METHYL PUTYL 0.66 1.6298 -1.40C8 3.9005 11 82BUTYL BUTYL 0.33 2.7968 -2.6367 7.9071 11 82BUTYL OUTYL 0.50 2.0506 -1.7679 4.8542 11 82BUTYL BUTYL 0.66 1.5038 -1.3622 3.9500 11 82
A Temperatures in *C; absolute viscosities in cP.
As implied by eq. 7, the absolute viscosities did not exhibit Arrhenius
behavior. This is in contrast to the l-alkylpyridinium-AiClI melts, which
did obey the Arrhenius equation (over a somewhat smaller experimental temper-
ature range) (3). The viscosities of the imidazolium melts were "mirror
images" of their equivalent conductivities. Representative viscosities are
shown in Fig. 10. The dependence of viscosity on the size of the dialkylimid-
azolium cation is even more anomalous than the conductivity behavior. Figure
29
11 shows that MeEtImCl-AlCl3 melts have substantially lower viscosities
than do the other melts studied. The theoretical modeling of transport
pheiomena cited above includes modeling of absolute viscosities.
3.0 IiI l
S2.5 MOBU
MoPr B U t3 U
2.00
Me-) TEMPERATURE
S1.5
o2500
10*.1 50 00
75000 .5 ., l. IIIIlIJ
0.3 0.4 0.5 0.6 0.7
MOLE FRACTION AlC13
Fig. 10. Dependence of absolute viscosity on meltcompoitioa and temperature.
The experimental specific conductivities of the ternary melts (including
those presented in Table IV) were least squares fitted to eq. 5, and the
resulting parameters are given in Table IX, togcther with the valid tempera-
ture range for each composition. Addition of the relatively polar molecules
acetonitrile and propionitrile to MeEtImCl-AlCI 3 binaries increased the
specific conductivity. Butyronitrile produced a smaller but still significa'nt
improvement in conductivity. The conductivity increases presumibly were due
to the lowering of melt viscosities; viscosities of the te-nary melts have not
been measured, but the solutions appeared to the eye noticeably more fluid
when they were handled.
30
I II
11 TEMPERATURE 60 OC01
MOL.E FRACTION AIC13 :0.50
Bu-u
S1.0! 0 Musu
MeMeI•Il
OgLi... MeEt3//'LF•~O•o306
0.8_ _ __I_ _ _ _I I I
2 3 4 5 6 7 8
NUMBER OF ALKYL GROUP CARBONS
Fig. 11. Dependence of absolute viscosity on imidazoliumcation size.
Additions of benzene had veiy little effect on conductivity, and xylene
significantly lowered the conductivity. Only small amounts of LiCi markedly
lowered the specific conductivity. Some of these effects may be seen in Fig.
12.
The organic cosolvents appeared to be soluble over large composition
regions. They apparently were miscible in all proportions with the equimolar
MeEtImCl-AlCl 2 binary melt at room temperature. The nitriles were mis-
cible in all proportions with N - 0.33 melts. An immiscibility region was
observed from 0.10 > X3 > 0.33 for propionitrile in the N = 0.66 binary
melt. In basic melts LiCl was the only alkali chloride that had a substantial
solubility (up to 0.1 mole fraction). In acidic melts all of the alkali
chlorides were soluble up to at least 0.1 mole fraction, but many of the
31
resulting ternaries were no longer liquid at room temperature. Alkali chlor-
ide solubilities were sharply reduced in equimolar melts.
Table IX. Least Squares Fitted Parameters for Ternary Melt SpecificConductivities.a
THIRD COMPONENT N X3 KOX10 KIX1X K2 XlI Tmin Tmax
ACETONITRILE 0.33 0.72 3.1083 5.4505 - 1B 80PROPIOMITRXLE 0.33 0.17 1.8436 4.5419 2.5903 14 leePROPIONITRILE 0.33 0.30 2.3086 5.0440 2.671S 31 leePROPIONITRILE 0.33 0.6S 4.3398 5.63S9 0.9570 28 100PROPIONITRILE 0.33 9.79 4.8528 4.9701 0.6041 21 99BUTYRONITRILE 0.33 0.14 1.4721 4.2394 3.4535 27 116BUTYRONITRILE 0.33 0.32 1.9577 4.6074 4.0041 28 100ACETONITRILE 0.50 0.7? 6.1811 7.5687 - 19 100ACETONITRILE 0.50 0.77 7.3380 8.0714 -0.2533 17 100ACETONITRILE 0.50 0.87 8.4408 9.1128 - 30 1o0ACETONITRILE 0.50 0.93 9.6865 8.7136 - 18 100PROPIONITRILE 0.50 0.21 5.2429 7.2817 1.4231 20 100PROPIONITRILE 0.50 0.36 5.9837 7.5e0o 1.0658 21 100PROPIONITRILE 0.50 0.75 7.S696 6.7759 -0.7188 17 100PROPIONITRILE 0.50 0.84 7.7976 6.4320 0.6093 1? 100PROPIONITRILE 0.50 0.91 6.6727 4.7537 1.0422 16 100BUTYRONITRILE 0.50 0.18 4.5765 7.0354 1.3607 29 100BUTYRONITRILE 0.50 0.31 4.8747 7.0043 1.3644 35 t0oBUTYRONITRILE 0.5e 0.64 5.6268 6.6056 O.5578 30 99BUTYRONITRILE 0.50 0.31 4.8351 5.1629 0.0991 30 19BENZENE 0-50 0.64 S.1047 6.8984 1.1378 is tooBENZENE 0.50 0.78 4.5274 4.8981 - 81 70BENZENE 0.50 0.8? 3.9348 3.8973 - 18 60XYLENE 0.50 0.03 4.2946 6.7084 1.8978 17 100XYLENE 0.50 0.23 4.2241 6.467s 1.4934 34 100XYLEME 0.50 0.73 3.524i 4.6637 - 85 t00XYLENE 0.60 0.27 3.4723 5.2782 1.4164 18 100PROPIONITRILE 0.66 0.28 2.6691 4.5585 1.4563 26 100PROPIONITRILE 0.66 0.88 5.6048 5.4898 0.1561 22 100
-Temperatures in deg. C; specific conductivities in ohm- cm-.
The greatest conductivity improvements were with acetonitrile and propio-
nitrile. At the highest temperatures reached in this study, acetonitrile
evaporated rapidly out of the liquid phase, but propionitrile did not. The
latter counlvent therefore was chosen as the "base-line" third component. A
detailed study is now underway of the density, conductivity, and viscosity of
propionitrile in MeEtImCl-AlCl 3 within the composition matrix 0.46 < N
< 0.54 and 0 < X3 < 0.75.
32
2 0.07 r 1 1 1 1 1 1 1 "
0.06- TEMPERATURE" 25° ACETONITRIL E
0• 0.05 - PROPIO NITRILE,,d
0.04 -MOLE FRACTION AICI 3
-- ~IN B•N A .Y
o .BUTYRONITRILEz 0. 0 2r0
o 0.01 L
L MeEtImCl-AICI 3 BINARIESL) O 0 - iI I I I I
a. 0.0 0.2 0.4 0.6 0.8 1.0MOLE FRACTION OF THIRD COMPONENT
Fig. 12 Specific conductivity of ternary melts.
33
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