Phase Equilibria of 1-hexyl-3-methylimidazolium acetate with water and oil

Fluid Phase Equilib ia
Accep ed e sion o he manusc ip : h ps://doi.o g/10.1016/j. luid.2018.11.010
Phase Equilib ia o 1-hexyl-3-me hylimidazolium ace a e wi h
wa e and oil
R. Co che o, I. Rod íguez-Escon ela, O. Rod íguez, A. So o*
Depa men o Chemical Enginee ing, Uni e sidade de San iago de Compos ela, E-
15782 San iago de Compos ela, Spain
*ana.so [email protected]
ABSTRACT
Ionic liquids ha e inc eased he possibili ies o Enhanced Oil Reco e y (EOR) wi h
su ac an s. Howe e , esul s ob ained wi h only one o hese sal s as su ac an a e no
pa icula ly p omising. Bes esul s a e ob ained wi h blends o hese sal s o blends
wi h adi ional su ac an s. This wo k aims o b eak new g ound ega ding he ole o
ionic liquids in his applica ion. Many adi ional su ac an s in EOR ail because hey
a e no su icien ly soluble a op imal salini y in wa e . The possibili ies o design o
ionic liquids mus also be conside ed o use hem as co-su ac an s in op imal
o mula ions o oil eco e y. In his wo k, he phase beha iou o he ionic liquid 1-
hexyl-3-me hylimidazolium ace a e wi h wa e and di e en model oils (n-oc ane,
cyclohexane and oluene) was de e mined a 298.15 K and 323.15 K. The comple e
miscibili y o he ionic liquid wi h wa e and i s low miscibili y wi h he di e en oils,
poin o he use o 1-hexyl-3-me hylimidazolium ace a e as co-su ac an wi h
su ac an s wi h high oil solubilising capaci y.
Keywo ds: Ionic Liquid; Wa e ; Oil; Equilib ium; EOR.
1. In oduc ion
In oil eco e y, a he end o wa e looding, he esidual oil is in he o m o immobile
globules dis ibu ed h ough he po es o he ocks. An ul a-low in e acial ension
be ween c ude oil and aqueous phases is equi ed o allow he oil mobilisa ion and
enhance oil eco e y. This can be achie ed in he p esence o a sui able su ace ac i e
agen . Su ac an Enhanced Oil Reco e y (EOR) is based on a mul icomponen
mul iphase sys em, gene a ed by he injec ion o an op imal o mula ion, whose
displacemen is complica ed by ac o s o phase beha iou , dispe sion, and adso p ion.
Su ac an solu ion phase beha iou is s ongly a ec ed by he p esence o sal in he
ese oi . A a low salini y, he su ac an is soluble in he aqueous phase and some oil
is solubilised in he co e o he micelles. A lowe -phase mic oemulsion is o med in
equilib ium wi h an excess oil phase essen ially ee o su ac an . A high salini y, he
sys em sepa a es in an oily uppe -phase mic oemulsion in equilib ium wi h an excess
wa e phase. A some in e media e salini y, he sys em o ms h ee phases; an excess oil
phase, a middle-phase mic oemulsion whe e he su ac an solubilises equi alen weigh
o wa e and oil, and an excess wa e phase [1]. This salini y is conside ed op imal
because i p oduces he lowes in e acial ension.
Many su ac an s ha show ul a-low in e acial ension and excellen mic oemulsion
phase beha iou wi h c ude oils a e no su icien ly soluble a op imal salini y o gi e
clea , s able, aqueous solu ions [2]. Poo su ac an solubili y may esul in e y high
su ac an e en ion in he well. The use o hyd ophilic co-sol en s o co-su ac an s
helps o dissol e he su ac an in he b ine and o educe su ac an e en ion.
Mo eo e , he use o hese compounds could be a key ac o o p omo ing good phase
beha iou du ing a su ac an looding ope a ion.
One o he main ad an ages o Ionic liquids (ILs) is ha hey can be ailo ed o ha e a
speci ic p ope y o o be used in a speci ic applica ion [3]. Wi h his in mind, some
esea che s ha e p oposed he use o su ace ac i e ILs as su ac an s o EOR [4-7].
Be a and Belhaj [4] p esen a s a e o he a - e iew o he use o ILs as al e na i es o
su ac an s in EOR. Se e al ILs ha e been ound ac i e in educing in e acial ension
as well as changing he ese oi ock su ace we abili y, howe e up o now an ul a-
low in e acial ension (10-3 mN/m) has no been achie ed using a single IL. Recen ly,
some wo ks p opose he use o blends o ILs and adi ional su ac an s [8,9].
Rod íguez-Escon ela e al. [8] p opose he use o a blend IOS15-58/1-dodecyl-3-
me hylimidazolium b omide (mass a io=8/2). A low equilib ium in e acial ension o
~2ꞏ10-3 mN/m was ob ained be ween n-oc ane and seawa e . Jia e al. [9] p opose he
blend n-dodecyl-n-me hylpy olidinium b omide/SDS (mola a io o 1:2.5) ob aining
an in e acial ension o ∼4×10−3 mN/m be ween model oil (n-decane o oluene) and
wa e .
The wo k on ILs as co-su ac an s in combina ion wi h adi ional su ac an s o EOR
applica ions has no p ac ically s a ed. Only one ecen wo k was ound in li e a u e
[10] whe e hese sal s a e used wi h adi ional su ac an s o dec ease su ac an
adso p ion on o c ushed co e samples. The use o hese sal s as co-su ac an s in EOR
o mula ions could imp o e he solubili y o he su ac an in he injec able aqueous
solu ion, a oid su ac an e en ion and inc ease oil eco e y. They also could allow
slugs o be ailo ed o high salini y and empe a u e. Mo eo e , as ILs a e sal s, hey
could be used o modi y he op imal salini y o a su ac an leading o a change in phase
beha iou . Fo hese easons, his esea ch should be encou aged.
As a i s s ep in he analysis o he possibili ies o using he ionic liquid 1-hexyl-3-
me hylimidazolium ace a e ([C6mim][OAc]) as co-su ac an in EOR, in his wo k, he
phase beha iou o he a o emen ioned IL wi h wa e and di e en model oils (n-oc ane,
cyclohexane and oluene) is de e mined a 298.15 K and 323. 15 K. Da a a e co ela ed
o each e na y sys em and all he da a se s wi h he Non-Random Two Liquid ac i i y
coe icien model [11]. The consis ency o he bina y coe icien s ob ained is es ed
acco ding o he me hod o Ma cilla e al. [12].
2. Expe imen al
2.1 Chemicals
In o ma ion abou all he chemicals used in his wo k can be ound in Table 1. Wa e
was pu i ied ia double dis illa ion. Se e al o ganic compounds we e used o mimic
di e en oils. n-Oc ane and oluene wi h nominal pu i ies >99.9 w % and >99.5 w %,
espec i ely, we e pu chased om Sigma-Ald ich. Cyclohexane wi h a nominal pu i y
>99.5 w % was pu chased om Riedel-de Haën. All hese chemicals we e used as
ecei ed, wi h he only p ecau ion o ha ing molecula sie es in o he bo les o d ying
he o ganic sol en s.
1-Hexyl-3-me hylimidazolium ace a e was syn hesised in ou labo a o y by me a hesis
eac ion. 1-hexyl-3-me hylimidazolium chlo ide (Sigma-Ald ich, >97%) and po assium
ace a e (Sigma-Ald ich, 99%) we e used as eac an s. They we e le o eac in 2-
p opanol (Pan eac, >99.8%) o 48 hou s unde s i ing. A p ecipi a e (KCl) was
emo ed ia il a ion. The ola ile sol en was emo ed by means o a o a y
e apo a o . The sample was dissol ed se e al imes in cold ace one (Sigma-Ald ich,
ACS eagen , >99.5%) and il e ed un il he o al elimina ion o KCl. A e his p ocess,
no p ecipi a ion was obse ed upon addi ion o 0.1 M aqueous solu ion o sil e ni a e
o an aqueous solu ion o he ionic liquid. The absence o ele an le els o impu i ies
was e i ied by 1H and 13C nuclea magne ic esonance (NMR) spec oscopy analyses.
2.2 Me hods
In o de o check i he ionic liquid [C6mim][OAc] had su ac an cha ac e , he su ace
ension o aqueous solu ions o he sal was measu ed looking o a c i ical micelle
concen a ion. The Wilhelmy pla e me hod was used by means o a K üss K11
ensiome e . A pla inum cylinde (K üss accesso y e e ence PL22) was used o
measu emen s. Tempe a u e was kep cons an wi h a Selec a F igi e m-10 c yogenic
he mos a . The unce ain y in he measu emen o empe a u e is 0.05K. Each sample
was analysed a leas wo imes (mo e i he esul s showed de ia ions g ea e han
unce ain y), wi h wel e consecu i e measu emen s o each sample ( he i s wo we e
sys ema ically dis ega ded). The es ima ed unce ain y is 0.3 mN/m.
To de e mine he expe imen al liquid-liquid equilib ium o he e na y sys ems, i s ly
he cloud-poin me hod was used o ob ain he solubili y cu es. Mix u es, wi h
composi ions inside hese cu es, we e mixed in jacke ed essels. The mix u es we e
magne ically s i ed o 2 h and hen se led down o a minimum o 12 h, a a ixed
empe a u e main ained by means o a Selec a Ul a e m 200 he mos a ic ba h.
P elimina y es s we e ca ied ou o ensu e ha hese imes we e enough o ensu e
equilib ium. Samples we e wi hd awn and analysed by gas ch oma og aphy. A Hewle -
Packa d HP6890 se ies GC was used wi h a spli injec o , a TCD de ec o , and a HP-
FFAP (25 m x 0.2 mm x 0.33 m) capilla y column. An emp y p e-column was used o
p e en ionic liquid no e ained in he line eaching he analy ical column. Helium was
used as he mobile phase and he injec ion olume was 1 mL wi h a spli a io o 1:50.
The injec o and de ec o empe a u e we e se o 523.15 K and 503.15 K espec i ely.
The o en empe a u e p og am was s a ed a 333.15 K (5 minu es o n-oc ane and
cyclohexane sys ems, and 7 minu es o oluene sys em), ollowed by a empe a u e
amp a 75 K min−1 up o 473.15 K, his empe a u e was kep cons an o 1 min.1-
Bu anol was used as diluen and 2-p opanol as s anda d. Ch oma og aphic analysis
allowed he de e mina ion o wa e and oil mass ac ions, ollowing he p epa a ion o
calib a ion cu es, and in his way he composi ion o he e na y mix u e was
calcula ed. The negligible IL con en in he oil phase de e mined by ch oma og aphy
was also con as ed by using ICP (op ical) spec oscopy
3. Resul s
In a p e ious wo k [13], he possibili y o using he ionic liquid [C12mim][OAc] as
su ac an o EOR was analysed. I was ound ha his su ac an could d as ically
educe he in e acial ension wa e /oil, howe e he alues ob ained o his p ope y
we e ound a om he ul a-low alues equi ed in EOR. Thus, he idea o using hese
ionic liquids as co-su ac an s a he han su ac an s came up. Blesic e al. [14] showed
ha [Cnmim]Cl ionic liquids wi h n>8 o m micella agg ega es in wa e . Fo n<8 hese
sal s do no show an in e acial ension pla eau which indica es ha he hyd ophobici y
is no su icien o build up micelles in hese cases. A simila beha iou was expec ed
o [Cnmim][OAc] ionic liquids.
In his wo k he e o e, since he use o 1-me hyl-3-alkylimidazolium ace a e ionic liquid
is p oposed as co-su ac an , an alkyl chain leng h six ca bon uni s long was selec ed.
To con i m ha [C6mim][OAc] does no ha e su ac an cha ac e , he su ace ension
o aqueous solu ions a se e al concen a ions o he ionic liquid was ep esen ed
(Figu e 1). As a pla eau in su ace ension is no obse ed, as expec ed, he ionic liquid
is no a su ace ac i e agen . The alues o he su ace ension a e p esen ed in Table 2.
Tables 3 o 8 show he liquid-liquid equilib ium o he e na y sys ems wa e +
[C6mim][OAc] + hyd oca bon (n-oc ane, oluene and cyclohexane) a 298.15 K and
323.15 K and 0.1 MPa. The wa e + [C6mim][OAc] pai is o ally miscible a bo h
empe a u es. Wi hin unce ain ies o analysis he pai wa e + hyd oca bon is o ally
immiscible, wha is in good ag eemen wi h p e ious s udies ha show mu ual
solubili ies o hese compounds in he o de o ppm [15]. Also he solubili y o
[C6mim][OAc] in he hyd oca bons is ound o be negligible. This is consis en wi h
s udies ca ied ou by Song e al. [16] who measu ed solubili ies o he ionic liquid in

n-oc ane, oluene and cyclohexane a 298.15 K, ob aining alues o 99, 643 and 124
ppm, espec i ely. Rega ding he e na y sys ems, hey show biphasic egions whe e he
uppe phase consis s o only o ganic sol en .
Tables 3 and 4 show he liquid-liquid equilib ium o he e na y sys em wa e +
[C6mim][OAc] + n-oc ane a 298.15 K and 323.15 K, espec i ely. Figu es 2 and 3
show ha hese sys ems can be classi ied as T eybal ype II due o he pa ial miscibili y
o he wa e + n-oc ane and [C6mim][OAc] + n-oc ane pai s. Inc easing he
empe a u e, he solubili y o n-oc ane in he ionic liquid sligh ly inc eases. Howe e
p ac ically all he e na y mix u es, a bo h empe a u es, o m biphasic sys ems
consis ing o one pu e oil phase and he o he an aqueous solu ion o he ionic liquid.
Da a o he e na y sys em o ionic liquid wi h wa e and oluene a e p esen ed in
Tables 5 and 6 and shown in Figu es 4 and 5. Phase diag ams o his oil a e also
T eybal ype II. Howe e , he in e ac ions be ween he a oma ic ing o he imidazolium
and oluene lead o a highe solubili y o he oluene han n-oc ane in he ionic liquid. A
solubili y o oluene in he ionic liquid o 0.349 (mass ac ion) is ound a 298.15 K
ha inc eases up o 0.357 a 323.15 K.
Phase diag ams o wa e + [C6mim][OAc] + cyclohexane e na y sys em a 298.15 K
and 323.15 K and 0.1 MPa a e shown in Figu es 6 and 7, espec i ely. Mass
composi ions o he ends o he ie-lines a e shown in Tables 7 and 8. As in he case o
n-oc ane, he phase diag am can be classi ied as a T eybal Type II sys em, and due o a
low solubili y o he cycloalkane in he ionic liquid, he ie-lines co e up almos he
whole e na y diag am.
4. Da a ea men
4.1 Da a co ela ion
Mole ac ions a e co ela ed using he NRTL [11] ac i i y coe icien model. The alue
o he non- andomness pa ame e

is p e- ixed a 0.1, 0.2 and 0.3, and he alue ha
achie es he minimum de ia ions om expe imen al da a is selec ed. 
Following he me hod o S ensen and A l [17], wo objec i e unc ions a e used in he
co ela ion. Fi s , Fa, which does no equi e any p e ious guess o pa ame e s, and
a e con e gence hese pa ame e s a e used in he second unc ion, Fb, o minimise
de ia ions in mole ac ions:
𝐹∑∑
󰇟󰇛𝑎
𝑎
󰇜/󰇛𝑎
𝑎
󰇜󰇠𝑄∑𝑃

 (1)
𝐹∑𝑚𝑖𝑛
∑∑󰇛𝑥 𝑥󰇜
 𝑄∑𝑃

 (2)
a: ac i i y; x: mole ac ion; Pn: adjus able pa ame e s; Q: penal y e m, 10−6 in Eq (1)
and 10−10 in Eq. (2); i: componen s; j: phases (I, II); k ie-lines; ^ means calcula ed.
De ia ions o he co ela ions a e de e mined acco ding o:
𝐹100 󰇣∑𝑚𝑖𝑛∑∑󰇛
󰇜

 󰇤.
(3)
M: numbe o ie-lines.
NRTL pa ame e s and F de ia ions o all he e na y sys ems (α op imised) a 298.15
K and 323.15 K a e p esen ed in Tables 9-11 o n-oc ane, oluene, and cyclohexane,
espec i ely. These ables also show he esul s o he simul aneous co ela ion a bo h
empe a u es. Resul s (also shown g aphically in Figu es 2 o 7) demons a e ha his
ac i i y coe icien model adequa ely co ela e hese equilib ia. When he simul aneous
co ela ion a bo h empe a u es is ca ied ou , highe de ia ions a e ound, pa icula ly
no iceable in he case o he sys em wi h oluene. As hese sys ems sha e he bina y
sys em wa e + [C6mim][OAc] and he co ela ion pa ame e s o his sys em should be
common, a simul aneous co ela ion o all he sys ems a bo h empe a u es is ca ied
ou and esul s a e shown in Table 12. A de ia ion in composi ions o 0.017 is ound in
his case.
4.2 Consis ency o co ela ion pa ame e s
The me hod and so wa e p oposed by Ma cilla e al. [12] is used o es he consis ency
o he NRTL co ela ion pa ame e s o each e na y sys em. The mino common
angen c i e ion is he necessa y and su icien condi ion o sol ing phase equilib ia,
hus he opology analysis o he Gibbs ene gy cu e o he mix u e (GM) allows he
consis ency o co ela ion pa ame e s o be easily checked. Figu e 8 show he esul s
ob ained wi h he so wa e p esen ed in he abo e men ioned pape o all he e na y
sys ems a 298.15 K.
Fo he wa e (1) + [C6mim][OAc] (2) miscible bina y subsys em, no common angen
line o he Gibbs ene gy cu e o he mix u e (GM) exis s. Fo [C6mim][OAc] (2) + n-
oc ane/ oluene/cyclohexane (3) bina y subsys ems ha a e pa ially miscible, one mino
common angen line ha co esponds wi h he calcula ed LLE ie-line exis s. Figu e 8
con i ms he consis ency be ween he calcula ed ie-lines and he GM su ace ob ained
wi h he pa ame e s shown in Tables 9 o 11.
Miscible (L) and pa ially miscible (LL) egions and bounda y we e also calcula ed
(Figu e 7), using he NRTL model, as a unc ion o he dimensionless conjuga ed bina y
pa ame e s [18], and he esul s a e in ag eemen wi h expe imen al e idence.
Conclusions
The ionic liquid [C6mim][OAc] does no possess su ac an cha ac e . As a p elimina y
s udy on he possibili y o using his sal as co-su ac an in su ac an o micella
looding EOR p ocesses, he beha iou o his ionic liquid wi h wa e and di e en
kinds o oils was s udied.
The wa e + [C6mim][OAc] pai is comple ely miscible which is an impo an
ad an age ocusing on he p epa a ion o op imal o mula ions o EOR. The ionic
liquid could be he base o p epa e clea aqueous solu ions o su ac an s, hus a oiding
he p oblems associa ed wi h alcohols ha a e usually selec ed as co-su ac an s.
[C6mim][OAc] is able o solubilise a ce ain quan i y o oluene bu i s miscibili y wi h
n-oc ane and cyclohexane is e y limi ed. Wi h a small quan i y o wa e added, he
sys em spli s in o wo phases. Phase diag ams ob ained poin o he use o his ionic
liquid wi h a su ac an wi h high capaci y o solubilise oil.
As equilib ium da a can be use ul o di e en applica ions, he e na y liquid-liquid
equilib ia ob ained we e co ela ed wi h he NRTL equa ion ob aining low de ia ions.
Mo ing om he co ela ion o one e na y sys em o he simul aneous co ela ion o all
da a se s allowed he ep esen a ion o all phase diag ams wi h a single se o
pa ame e s. The penal y o such co ela ion is an inc ease on he de ia ion om
expe imen al concen a ions up o 1.7 mol%.
Acknowledgemen s
The au ho s acknowledge he Minis y o Economy and Compe i i eness (Spain) o
inancial suppo h oughou p ojec CTQ2015-68496-P (including Eu opean Regional
De elopmen Fund ad anced unding).
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Table 6. Liquid-liquid equilib ium o he e na y sys em wa e (1) + [C6mim][OAc] (2)
+ oluene (3) a 323.15 K and 0.1 MPa.
S anda d unce ain ies: u(P) = 5 kPa, u(T) = 0.05 K
Uppe phase Lowe phase
w1 w
2 w
3 w
1 w
2 w
3
0.000 0.000 1.000 1.000 0.000 0.000
0.000 0.000 1.000 0.849 0.148 0.003
0.000 0.000 1.000 0.706 0.289 0.005
0.000 0.000 1.000 0.577 0.413 0.010
0.000 0.000 1.000 0.378 0.589 0.033
0.000 0.000 1.000 0.247 0.684 0.069
0.000 0.000 1.000 0.105 0.737 0.158
0.000 0.000 1.000 0.000 0.643 0.357
u(w1)=0.001 u(w2)=0.001 u(w3)=0.001 u(w1)=0.002 u(w2)=0.003 u(w3)=0.003

Table 7. Liquid-liquid equilib ium o he e na y sys em wa e (1) + [C6mim][OAc] (2)
+ cyclohexane (3) a 298.15 K and 0.1 MPa.
Uppe phase Lowe phase
w1 w
2 w
3 w
1 w
2 w
3
0.000 0.000 1.000 1.000 0.000 0.000
0.000 0.000 1.000 0.892 0.108 0.000
0.000 0.000 1.000 0.815 0.185 0.000
0.000 0.000 1.000 0.679 0.318 0.003
0.000 0.000 1.000 0.556 0.440 0.004
0.000 0.000 1.000 0.428 0.564 0.008
0.000 0.000 1.000 0.365 0.624 0.011
0.000 0.000 1.000 0.228 0.750 0.022
0.000 0.000 1.000 0.108 0.850 0.042
0.000 0.000 1.000 0.000 0.954 0.046
u(w1)=0.001 u(w2)=0.001 u(w3)=0.001 u(w1)=0.003 u(w2)=0.003 u(w3)=0.001
Table 8. Liquid-liquid equilib ium o he e na y sys em wa e (1) + [C6mim][OAc] (2)
+ cyclohexane (3) a 323.15 K and 0.1 MPa.
S anda d unce ain ies: u(P) = 5 kPa, u(T) = 0.05 K
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Uppe phase Lowe phase
w1 w
2 w
3 w
1 w
2 w
3
0.000 0.000 1.000 1.000 0.000 0.000
0.000 0.000 1.000 0.886 0.114 0.000
0.000 0.000 1.000 0.805 0.195 0.000
0.000 0.000 1.000 0.645 0.351 0.004
0.000 0.000 1.000 0.514 0.480 0.006
0.000 0.000 1.000 0.428 0.563 0.009
0.000 0.000 1.000 0.354 0.633 0.013
0.000 0.000 1.000 0.234 0.741 0.025
0.000 0.000 1.000 0.114 0.841 0.045
0.000 0.000 1.000 0.000 0.953 0.047
u(w1)=0.001 u(w2)=0.001 u(w3)=0.001 u(w1)=0.003 u(w2)=0.003 u(w3)=0.001
Table 9. Bina y in e ac ion pa ame e s and esidual unc ion o he co ela ions o he
e na y sys em wa e (1) + [C6mim][OAc] (2) + n-oc ane (3).
Tempe a u e
(K) Pa ame e s (alpha=0.2) De ia io
n
298.15 K
u12 (J/mol) -1008.0 u21 (J/mol) -1147.3
F=0.17
u13 (J/mol) 10965 u31 (J/mol) 11229
u23 (J/mol) 3591.7 u32 (J/mol) 11071
323.15 K
u12 (J/mol) -1373.9 u21 (J/mol) -1227.8
F=0.18
u13 (J/mol) 11406 u31 (J/mol) 12210
u23 (J/mol) 3437.3 u32 (J/mol) 12384
Bo h
u12 (J/mol) -1488.3 u21 (J/mol) -1397.0
F=0.30
u13 (J/mol) 11602 u31 (J/mol) 12566
u23 (J/mol) 3475.6 u32 (J/mol) 12557
Table 10. Bina y in e ac ion pa ame e s and esidual unc ion o he co ela ions o he
e na y sys em wa e (1) + [C6mim][OAc] (2) + oluene (3).
Tempe a u e Pa ame e s (alpha=0.3) De ia io
n
298.15 K
u12 (J/mol) -5438.8 u21 (J/mol) -6698.9
F=0.16
u13 (J/mol) 13212 u31 (J/mol) 14993
u23 (J/mol) 3812.2 u32 (J/mol) 11012
323.15 K
u12 (J/mol) -6538.6 u21 (J/mol) -7918.3
F=0.18
u13 (J/mol) 13843 u31 (J/mol) 16503
u23 (J/mol) 4066.6 u32 (J/mol) 11820
Bo h
u12 (J/mol) -6222.9 u21 (J/mol) -7376.2
F=0.26
u13 (J/mol) 14421 u31 (J/mol) 16961
u23 (J/mol) 4084.4 u32 (J/mol) 12364
Table 11. Bina y in e ac ion pa ame e s and esidual unc ion o he co ela ions o he
e na y sys em wa e (1) + [C6mim][OAc] (2) + cyclohexane (3).
Tempe a u e Pa ame e s (alpha=0.2) De ia io
n
298.15 K
u12 (J/mol) -1769.5 u21 (J/mol) -1644.5
F=0.24
u13 (J/mol) 9539.9 u31 (J/mol) 11470
u23 (J/mol) -3934.1 u32 (J/mol) 16832
323.15 K
u12 (J/mol) -2917.9 u21 (J/mol) -451.50
F=0.21
u13 (J/mol) 10858 u31 (J/mol) 11865
u23 (J/mol) -4412.6 u32 (J/mol) 18631
Bo h
u12 (J/mol) -7180.5 u21 (J/mol) -694.70
F=0.68
u13 (J/mol) 10176 u31 (J/mol) 12068
u23 (J/mol) -4063.3 u32 (J/mol) 16720
Table 12. Bina y in e ac ion pa ame e s and esidual unc ion o he simul aneous
co ela ions o all he e na y sys ems.
Pa ame e s (alpha=0.2) De ia io
n
uW-IL (J/mol) -12595 uIL-W (J/mol) 478.20
1.74
uW-O (J/mol) 11699 uO-W (J/mol) 12386
uIL-O (J/mol) 3465.0 uO-IL (J/mol) 12545
uW-T (J/mol) 9082.8 uT-W (J/mol) 12411
uIL-T (J/mol) 1600.2 uT-IL (J/mol) 15744
uW-C (J/mol) 10417 uC-W (J/mol) 12628
uIL-C (J/mol) -3956.6 uC-IL (J/mol) 16117
W: Wa e ; IL: Ionic Liquid; O: n-Oc ane; T: Toluene; C: Cyclohexane
w %
0.001 0.010 0.100 1.000 10.000 100.000
 (mN/m)
30
35
40
45
50
55
60
65
70
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Figu e1:Su ace ensionas unc iono [C6mim][OAc]concen a ioninaqueoussolu ion.
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n-oc ane
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
[C6mim][OAc]
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Wa e
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Expe imen al da a
NRTL co ela ion
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Figu e2:LLEo  he e na ysys emwa e +[C6mim][OAc]+n‐oc anea 298.15Kand0.1MPa.
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n-oc ane
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
[C6mim][OAc]
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Wa e
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Expe imen al da a
NRTL co ela ion
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Figu e3:LLEo  he e na ysys emwa e +[C6mim][OAc]+n‐oc anea 323.15Kand0.1MPa.
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Toluene
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
[C6mim][OAc]
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Wa e
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Expe imen al da a
NRTL co ela ion
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Figu e4:LLEo  he e na ysys emwa e +[C6mim][OAc]+ oluenea 298.15Kand0.1MPa.
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Toluene
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
[C
6
mim][OAc]
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Wa e
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Expe imen al da a
NRTL co ela ion
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Figu e5:LLEo  he e na ysys emwa e +[C6mim][OAc]+ oluenea 323.15Kand0.1MPa.
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