ene gies
A icle
Simul aneous Ex ac ion and Emulsi ica ion o Food
Was e Lique ac ion Bio-Oil
Da id Längaue 1,2 , Yu-Ying Lin 2, Wei-Hsin Chen 2,3,* , Chao-Wen Wang 2, Michal Ša ᡠ1,2
and Vladimí ˇ
Cablík1
1Ins i u e o En i onmen al Enginee ing, Facul y o Mining and Geology, VŠB—Technical Uni e si y o
Os a a, 17. lis opadu 15, 708 33 Os a a-Po uba, Czech Republic; [email p o ec ed] (D.L.);
[email p o ec ed] (M.Š.); ladimi [email p o ec ed] (V. ˇ
C.)
2Depa men o Ae onau ics and As onau ics, Na ional Cheng Kung Uni e si y, Tainan 701, Taiwan;
[email p o ec ed] (Y.-Y.L.); [email p o ec ed] (C.-W.W.)
3
Resea ch Cen e o Ene gy Technology and S a egy, Na ional Cheng Kung Uni e si y, Tainan 701, Taiwan
*Co espondence: [email p o ec ed] o [email p o ec ed]; Tel.: +886-6-2004456
Recei ed: 6 Oc obe 2018; Accep ed: 31 Oc obe 2018; Published: 5 No embe 2018


Abs ac :
Biomass-de i ed bio-oil is a sus ainable and enewable ene gy esou ce, and lique ac ion is
a po en ial con e sion way o p oduce bio-oil. Emulsi ica ion is a physical upg ading echnology,
which blends immiscible liquids in o a homogeneous emulsion h ough he addi ion o an emulsi ie .
Lique ac ion bio-oil om ood was e is cha ac e ized by i s high pou poin when compa ed o diesel
uel. In o de o pa ially eplace diesel uel by lique ac ion bio-oil, his s udy aimed o de elop a
me hod o simul aneously ex ac and emulsi y he bio-oil using a comme cial su ac an (A lox 4914,
CRODA, Snai h, UK). The solubili y and s abili y o he emulsions a a ious ope a ing condi ions
such as he bio-oil- o-emulsi ie a io (B/E a io), s o age empe a u e and du a ion, and co-su ac an
(me hanol) addi ion we e analyzed. The esul s demons a e ha highe amoun s o bio-oil (7 g)
and emulsi ie (7 g) a a B/E a io = 1 in an emulsion ha e a highe solubili y (66.48 w %). When
he B/E a io was dec eased om 1 o 0.556, he bio-oil solubili y was enhanced by 45.79%, e en
hough he s o age du a ion was up o 7 days. Compa ed o he emulsion s o ed a oom empe a u e
(25
◦
C), i s s o age a 100
◦
C p esen ed a highe solubili y, especially a highe B/E a ios. Mo eo e ,
when me hanol was added as a co-su ac an du ing emulsi ica ion a highe B/E a ios (0.714 o 1),
i ende ed be e solubili y (58.83–70.96 w %). O e all, he emulsi ied oil showed g ea e s abili y
a e he ex ac ion-emulsi ica ion p ocess.
Keywo ds: emulsi ica ion; lique ac ion; bio-oils; co-su ac an ; su ac an ; diesel
1. In oduc ion
In he 21s cen u y, ood was es in excess o one billion me ic ons a e gene a ed wo ldwide e e y
yea om a ious sou ces and such g ea amoun s lead o a se e e en i onmen al p oblem. Failu e o
ecycle o ea ood was es p ope ly will lead o he emission o me hane (CH
4
) and ca bon dioxide
(CO
2
) du ing bio-deg ada ion. These g eenhouse gases may cause human heal h and en i onmen al
p oblems [1].
In ecen yea s, he e has been an imp o emen in he mochemical con e sion equipmen , which
can ans o m was es in o bio uels o bioene gy p oduc s [
2
,
3
]. Food was e is conside ed a aluable
sou ce o ene gy due o i s high biodeg adabili y and high o ganic ma e con en [
4
,
5
]. Ne e heless,
he e is a g ea challenge in he con e sion o ood was es in o bio uels by adi ional he mochemical
con e sions such as py olysis and gasi ica ion. The high mois u e con en o ood was e equi es mo e
ime and ene gy o d ying be o e he con e sion p oceeds.
Ene gies 2018,11, 3031; doi:10.3390/en11113031 www.mdpi.com/jou nal/ene gies
Ene gies 2018,11, 3031 2 o 13
Hyd o he mal echnology (HTL) p o ides oppo uni ies o mo e ene gy e icien alo iza ion o
we biomass in ha wa e is used di ec ly as a eac ion medium, hus, bypassing he d ying p ocess [
6
,
7
].
A e HTL is pe o med, a sepa a ion p ocedu e is needed o ob ain he oil phase, also known as
he lique ac ion bio-oil. The sepa a ion me hod includes using a g a ime ic sepa a ion unnel o
ex ac ion wi h an o ganic sol en such as e ahyd o u an (THF), e hyl ace a e, and dichlo ome hane
(DCM) [
8
,
9
]. The lique ac ion bio-oil is a mix u e o se e al hund ed o ganic compounds such as acids,
alcohols, aldehydes, amides, es e s, ke ones, phenols, and lignin oligome s [
10
,
11
]. The lique ac ion
bio-oil has undesi able ea u es o indus ial applica ions such as a high iscosi y and high ash
con en . This implies ha he bio-oil composi ion is complex, making i ela i ely di icul o con ol
he pe o mance du ing he combus ion p ocess.
Emulsi ica ion is an e ec i e way o upg ading bio-oil and blending i wi h o he uels [
12
,
13
].
Emulsi ica ion echnology is popula o upg ading py olysis oil. Since diesel and bio-oil ha e pola
molecules, he emulsi ie o su ac an s can dispe se hem bo h o o m a s able and homogeneous
emulsion [
12
]. The emulsi ica ion o bio-oils o wa e in diesel using a ious emulsi ie s is summa ized in
Table 1. Michio [
14
] s udied he emulsion o diesel oil and py olysis oil om ha dwood and in es iga ed
he e ec s o i e ope a ion pa ame e s (bio-oil concen a ion, su ac an concen a ion, esidence ime,
mo o speed and emulsi ica ion empe a u e). The esul s we e op imized by a s a is ical model and he
dominan a iables we e iden i ied o minimal s a i ica ion o ma ion. These dominan pa ame e s
we e bio-oil concen a ion, and su ac an and powe inpu . Chia amon i [
15
] s udied diesel/bio-oil
emulsions wi h ou kinds o py olysis oils om Canadian oak, beech wood, Cali o nia pine, and
pine wood. The esul s sugges ed ha i is necessa y o use esh bio-oil and mic onize hese p oduc s
o ob ain a s able emulsion. Guo [
16
] used a KDL-5 molecula dis illa ion appa a us o sepa a e he
middle ac ion and he hea y ac ion o he c ude bio-oil. The blending o he diesel and bio-oil was
conduc ed by ul asonic and ul asonic-mechanical emulsi ica ion. The d ople size dis ibu ion was
measu ed using a Mal e n nanome e pa icle size analyze o he h ee emulsions (hea y ac ion
wi h 40–300 nm, middle ac ion wi h 15–60 nm and c ude bio-oil wi h 8–25 nm) and had he same
endency wi h he s abili y ime 14 min, 216 min and 31 days, espec i ely. As o he emulsion on
he lique ac ion bio-oil, Lijian. [
17
] employed mic o-emulsion echnologies o dissol e h ee kinds o
sewage sludge lique ac ion bio-oil ex ac ed by di e en sol en s in o diesel. The expe imen s showed
ha he bio-oils ob ained a a highe lique ac ion empe a u e (360 ◦C) bene i ed he mic o-emulsion.
Table 1. Li e a u e o bio-oil and lique ac ion oil in diesel emulsions.
Py olysis
Bio-Oil Con en Mixing Me hod Emulsi ie and Co-Su ac an S abili y Re .
10–30 w %
Mic o-emulsi ie
(800–1750 pm and
5–20 min)
Hype me B246SF/2234
(C oda In e na ional) 3 o 42 days [14]
25–75 w % Va iable speed elec ical
mo o (1100 W)
Polyme ic su ac an s/sho chain
addi i es (n-oc anol) 3 days [15]
10 w %
Ul asonic (20 kHz; 2 min)
and Ul asonic-mechanical
(20 kHz; 2 min; and
5000 pm; 5 min)
Span80 (so bi an monoolea e)/Tween
80 (Polyoxye hyleneso bi an
monolau a e)/Span 85
(so bi an iolea e)
27 o 31 days [16]
2–40 w % Homogenize
(8800–16,700 pm)
Span 80 (so bi an monoolea e)/Tween
80 (Polyoxye hyleneso bi an
monolau a e)
5 days [18]
Lique ac ion
Bio-Oil Con en Mixing Me hod Emulsi ie o Co-Su ac an S abili y Re .
5 w %
Manual shaking (1 min) and
cen i uga ion (6000 pm;
20 min)
Span 80 (so bi an monoolea e) - [17]
5 o 30 w % Vo ex mixe (3000 pm;
2 min)
A lox4914 (C oda
In e na ional)/Me hanol 7 days This
s udy
Ene gies 2018,11, 3031 3 o 13
Despi e some use ul in o ma ion p o ided om hese s udies, i should be unde lined ha he e
is s ill a lack o emulsi ica ion in o ma ion o he lique ac ion o bio-oil om ood was e. Mo eo e , he
mechanisms o ex ac ion and emulsi ica ion a e ela ed o he su ace ension, iscosi y, and pola i y
be ween he molecules [
15
–
17
]. Thus, his s udy aimed o in es iga e he easibili y o he simul aneous
emulsi ica ion-ex ac ion o he ood was e lique ac ion bio-oil and diesel wi h he addi ion o an
emulsi ie . This p ocess can combine lique ac ion bio-oil ex ac ion and emulsi ica ion in one s ep,
which can educe he expe imen cos and ime. The de ails o he p opo ion o he lique ac ion bio-oil
in he emulsion a e mixing wi h diesel a e also add essed.
2. Ma e ials and Me hods
2.1. Ma e ials
The aw lique ac ion bio-oil was p oduced om he hyd o he mal lique ac ion p ocess o ood
was e, which was collec ed om he local ood was e ecycling ield. I included hizomes and peels o
se e al kinds o ege ables and ui s, which we e ob ained om li elihood was e. Be o e he s a o
he lique ac ion p ocess, he size o he ood was e (800 g) was educed using a blende o in ensi y
he eac ion su ace a ea. The ood was e had a high mois u e con en (74%) o he lique ac ion
eac ion, hus, dismissing addi ional wa e . Then, he ood was e slu y was p e ea ed wi h a 5 w %
po assium ca bona e (K
2
CO
3
, alkali ca alys ) by hea ing he mix u e o 100
◦
C o 1 h. Subsequen ly,
he empe a u e was aised o 320
◦
C and held o 30 min as he condi ions o lique ac ion. The p ocess
yielded p oduc s a h ee di e en phases: gas, liquid, and solid. The wa e apo in he eac o was
emo ed by cooling o 105
◦
C unde a mosphe ic p essu e. The le o e liquid/solid mix u e was
hea ed o 100
◦
C o 4 h in he o en o emo e he excess wa e con en in he mix u e. Finally, he
emaining esidue was conside ed as he aw lique ac ion bio-oil ha ing an a e age con e sion a e
o 40 w %.
The diesel uel used o expe imen s was comme cially a ailable and sou ced om pe ol s a ion
o China Pe oleum Co po a ion (CPC). In he emulsi ica ion-ex ac ion p ocess, he lique ac ion oil
was dispe sed in o he diesel, leading o he bulk o he emulsion olume. The emulsi ie used in he
expe imen s was A lox 4914 ob ained om C oda In e na ional Plc. Me hanol (>99 ol %) was used as
he co-su ac an . The p ope ies o he bio-oil, diesel, A lox 4914, and co-su ac an such as densi y,
iscosi y, and highe hea ing alue (HHV) a e abula ed in Table 2.
Table 2. P ope ies o he bio-oil, diesel, su ac an , and co-su ac an .
Compound Densi y (kg m−3)Viscosi y (mPa s) HHV (MJ kg−1)
Bio-oil 1100.0 4916 31.41
Diesel 832.0 1.6–5.8 44.80
A lox 4914 970.0 - 37.64
Me hanol 791.0 0.533 20.40
2.2. The P ocedu e o P epa ing he Sample
To de e mine he minimum olume equi ed o he emulsi ie , a ixed quan i y o 20 g o diesel
was mixed wi h a ious amoun s o he emulsi ie (based on B/E a io) in a 50 mL cen i uge ube.
A o ex mixe (Model: VM-2000, Digisys em Labo a o y Ins umen s Inc., Taipei, Taiwan) was used
o mix he diesel and emulsi ie o 1 min a a speed o 3000 pm. The lique ac ion bio-oil was in he
o m o he solid phase a oom empe a u e, so i was p ehea ed o 100
◦
C in he o en o ans o m i
in o a liquid be o e he emulsi ica ion-ex ac ion p ocess. The ea e , he liquid aw lique ac ion bio-oil
was added in o he diesel-emulsi ie mix u e and mixed by he o ex mixe o 2 min a a speed o
3000 pm. Then, he emulsion samples we e s o ed a oom empe a u e (25
◦
C). Samples, which
needed highe - empe a u e condi ion, we e s o ed in an o en a 100
◦
C. The co-su ac an could educe
Ene gies 2018,11, 3031 4 o 13
he su ace ension o bio-oil and enhance he pe o mance o he emulsions [
13
]. The e o e, u he
emulsion expe imen s examined he e ec o he adjunc ion o he co-su ac an by adding one mo e
s ep in he p ocess o sample p epa a ion. A e he emulsions o diesel, emulsi ie , and bio-oil we e
p epa ed, me hanol was added and mixed o 1 min a a speed o 3000 pm. The de ailed p ocess is
shown in Figu e 1.
Ene gies 2018, 11, x FOR PEER REVIEW 4 o 13
emulsi ie , and bio-oil we e p epa ed, me hanol was added and mixed o 1 min a a speed o 3000
pm. The de ailed p ocess is shown in Figu e 1.
Figu e 1. Scheme o emulsion p epa a ion and s abili y analysis.
2.3. Analy ical Me hods
The e a e wo di ec ions o in es iga e he pe o mance o he ex ac ion-emulsi ica ion
expe imen : quan i a i e and quali a i e me hods. The quan i a i e esea ch is o iden i y he amoun
o bio-oil dissol ed in diesel. The deposi ed bio-oil is in he solid phase, so i is easy o sepa a e i
om he liquid emulsion and weigh he amoun . In o de o measu e he ex en o diesel-sol able
bio-oil, a pa ame e called solubili y was de ined as
Solubili y (%) = 𝑚𝑎𝑑𝑑𝑒𝑑 𝑏𝑖𝑜−𝑜𝑖𝑙 − 𝑚𝑖𝑛𝑠𝑜𝑙𝑣𝑎𝑏𝑙𝑒 𝑏𝑖𝑜−𝑜𝑖𝑙
𝑚𝑎𝑑𝑑𝑒𝑑 𝑏𝑖𝑜−𝑜𝑖𝑙
×100%
(1)
whe e 𝑚𝑎𝑑𝑑𝑒𝑑 𝑏𝑖𝑜−𝑜𝑖𝑙 s ands o he added mass o bio-oil and 𝑚𝑖𝑛𝑠𝑜𝑙𝑣𝑎𝑏𝑙𝑒 𝑏𝑖𝑜−𝑜𝑖𝑙 deno es he mass o
deposi ed bio-oil in he bo om o he ube.
Quali a i e esea ch is o e alua e he emulsion s abili y. Se e al me hods can be used such as
measu ing he pH alue, mois u e con en , he iscosi y o he emulsion, o d ople size dis ibu ion
in he emulsion [14,15]. Howe e , he e is no s anda d p ocedu e o examining he long- e m
s abili y [15]. In his s udy, Fou ie ans o m in a ed spec oscopy (FTIR) coupled wi h a enua ed
o al e lec ion (ATR) was used o examine he s abili y and homogenei y o he emulsions h ough
he iden i ica ion o he unc ional g oups p esen in he emulsions [12,13,19]. In some cases, e en
hough he emulsion seemed o be uni o m by isual inspec ion, he FTIR spec a we e di e en ,
e ealing he phase sepa a ion in he emulsion. Fo a homogeneous emulsion, he FTIR spec a a
di e en places would o e lap. The e o e, he emulsion was di ided in o h ee egions, namely, he
op, middle, and bo om liquid le els in he sample ube and he h ee egions we e analyzed using
FTIR [20].
Figu e 1. Scheme o emulsion p epa a ion and s abili y analysis.
2.3. Analy ical Me hods
The e a e wo di ec ions o in es iga e he pe o mance o he ex ac ion-emulsi ica ion
expe imen : quan i a i e and quali a i e me hods. The quan i a i e esea ch is o iden i y he amoun
o bio-oil dissol ed in diesel. The deposi ed bio-oil is in he solid phase, so i is easy o sepa a e i om
he liquid emulsion and weigh he amoun . In o de o measu e he ex en o diesel-sol able bio-oil, a
pa ame e called solubili y was de ined as
Solubili y (%)=madded bio−oil −minsol able bio−oil
madded bio−oil
×100% (1)
whe e
madded bio−oil
s ands o he added mass o bio-oil and
minsol able bio−oil
deno es he mass o
deposi ed bio-oil in he bo om o he ube.
Quali a i e esea ch is o e alua e he emulsion s abili y. Se e al me hods can be used such as
measu ing he pH alue, mois u e con en , he iscosi y o he emulsion, o d ople size dis ibu ion
in he emulsion [
14
,
15
]. Howe e , he e is no s anda d p ocedu e o examining he long- e m
s abili y [
15
]. In his s udy, Fou ie ans o m in a ed spec oscopy (FTIR) coupled wi h a enua ed
o al e lec ion (ATR) was used o examine he s abili y and homogenei y o he emulsions h ough he
iden i ica ion o he unc ional g oups p esen in he emulsions [
12
,
13
,
19
]. In some cases, e en hough
he emulsion seemed o be uni o m by isual inspec ion, he FTIR spec a we e di e en , e ealing he
Ene gies 2018,11, 3031 5 o 13
phase sepa a ion in he emulsion. Fo a homogeneous emulsion, he FTIR spec a a di e en places
would o e lap. The e o e, he emulsion was di ided in o h ee egions, namely, he op, middle, and
bo om liquid le els in he sample ube and he h ee egions we e analyzed using FTIR [20].
3. Resul s and Discussion
3.1. FTIR Spec a o A lox, Bio-Oil, Diesel, and Me hanol
FTIR analysis o he inpu componen s (A lox, ood was e lique ac ion bio-oil, diesel, and
me hanol) was pe o med and he spec a a e shown in Figu e 2. Diesel, me hanol, and A lox 4914 a e
comme cially a ailable subs ances wi h dis inc chemical composi ions. To iden i y he s a i ica ion o
he bio-oil in he emulsions, he chemical composi ion o he lique ac ion bio-oil was s udied. F om he
ob ained spec a and unc ional g oups summa ized in Table 3, he lique ac ion bio-oil con ained
C-H-(CH
2
) (732 cm
−1
), C-O (1034 cm
−1
), C-O (1258 cm
−1
), C-H-(CH
3
) (1414 cm
−1
), CH
3
(2918 cm
−1
),
and polyme ic O-H (3320 cm−1) unc ional g oups.
Ene gies 2018, 11, x FOR PEER REVIEW 5 o 13
3. Resul s and Discussion
3.1. FTIR Spec a o A lox, Bio-Oil, Diesel, and Me hanol
FTIR analysis o he inpu componen s (A lox, ood was e lique ac ion bio-oil, diesel, and
me hanol) was pe o med and he spec a a e shown in Figu e 2. Diesel, me hanol, and A lox 4914
a e comme cially a ailable subs ances wi h dis inc chemical composi ions. To iden i y he
s a i ica ion o he bio-oil in he emulsions, he chemical composi ion o he lique ac ion bio-oil was
s udied. F om he ob ained spec a and unc ional g oups summa ized in Table 3, he lique ac ion
bio-oil con ained C-H-(CH2) (732 cm−1), C-O (1034 cm−1), C-O (1258 cm−1), C-H-(CH3) (1414 cm−1), CH3
(2918 cm−1), and polyme ic O-H (3320 cm−1) unc ional g oups.
Figu e 2. FTIR spec a o (a) A lox, (b) bio-oil, (c) diesel, and (d) me hanol.
Wa eleng h (cm-1)
In ensi y (% T)
1000200030004000
60
65
70
75
80
85
90
95
100
(a) A lox 4914
850
3500
2954 2876 17341488
1353
1107
940
Wa eleng h (cm-1)
In ensi y (% T)
1000200030004000
60
65
70
75
80
85
90
95
100
(b) Food was e oil
1414
3320
2915
2858 1672
1034
1258 732
Wa eleng h (cm-1)
In ensi y (% T)
1000200030004000
60
65
70
75
80
85
90
95
100
(c) Diesel
722
2921
2853
1454
1376
Wa eleng h (cm-1)
In ensi y (% T)
1000200030004000
20
30
40
50
60
70
80
90
100
(d) Me hanol
722
3328
29482825 1437
1123
1023
Figu e 2. FTIR spec a o (a) A lox, (b) bio-oil, (c) diesel, and (d) me hanol.

Ene gies 2018,11, 3031 6 o 13
Table 3. Main unc ional g oups o emulsi ie s, co-su ac an s and lique ac ion bio-oil.
Wa e Numbe Range (cm−1)Func ional G oup Mode o Vib a ion Re e ence
3550–3450 Dime ic O-H S e ching [21]
3400–3230 Polyme ic O-H S e ching [21]
2949–2915 Alipha ic C-H S e ching [21,22]
2924–2858 Alipha ic C-H S e ching [23]
2835–2815 CH3-O-CH3(e he s) S e ching [21]
1740–1732 C=O (es e ) S e ching [23]
1651–1640 C=C (a oma ic) Skele al [24]
1652–1579 C-C ( ing) S e ching [21]
1486–1446 C-H- (CH3)/(CH2) Symme ic Asymme ic [24]
1461–1377 C-H- (CH3) Symme ic [24]
1290–1211 C-O S e ching [21]
1230–1140 C-O (phenol) S e ching [21]
1239–1100 C-O-C (es e ) S e ching [22,23]
1090–1049 C-O S e ching [21]
1043–1006 C-O S e ching [24]
970–960 C=C-H Bending [21]
730–710 C-H-(CH2) Bending [21]
3.2. Bio-Oil Solubili y and Emulsion S abili y a B/E Ra io = 1
By mixing a ious olume ic a ios o bio-oil/emulsi ie and obse ing he emulsion’s s abili y,
Figu e 3examines he solubili y o he bio-oil in he emulsions o e ime. In all cases, he B/E a io was
1 bu he e we e di e en amoun s o bio-oil and emulsi ie in he a ious samples in he emulsions.
In all ins ances, he e was an inc ease in he amoun o bio-oil in he sedimen o e ime. The solubili y
in all cases a 1 h du a ion was as high as a 70 w %, excep o he case o 1 g o bio-oil wi h
55.70 w
%.
The sepa a ion o bio-oil a e 1 day was signi ican in he case o 1 g bio-oil and only 16.61 w % o
i emained dissol ed in o he emulsion. Wi h an inc ease in s o age ime, he sedimen o he cases
in ol ing 1, 2, and 3 g o bio-oil became p onounced. Howe e , he solubili y o he cases in ol ing 4,
5, and 6 g o bio-oil wi h B/E = 1 emained abo e 55 w % on he 7 h day, implying ha he solubili y
o he emulsion imp o ed g ea ly when he amoun s o su ac an and bio-oil we e inc eased. On he
7 h day, he maximum solubili y in he case o 6 g bio-oil wi h B/E = 1 was 66.48 w %.
The FTIR spec a a h ee egions (i.e., op, middle, and bo om liquid le els in he ube) in
he emulsion unde 2 g bio-oil wi h B/E = 1 o 1 h o 7 days a e displayed in Figu e 4. The FTIR
spec a appea o almos o e lap and coincide wi h each o he , con i ming homogenei y and success ul
emulsi ica ion [12].
Ene gies 2018,11, 3031 7 o 13
Ene gies 2018, 11, x FOR PEER REVIEW 7 o 13
Figu e 3. The solubili y o he emulsions wi h di e en bio-oil amoun s (B/E = 1) (a) 1 h, (b) 1 day, (c)
3 days, (d) 5 days, and (e) 7 days.
Amoun o bio oil (g)
Solubili y (%)
0
20
40
60
80
100
1 2 3 4 5 6
(a) 1 h
Amoun o bio oil (g)
Solubili y (%)
0
20
40
60
80
100
1 2 3 4 5 6
(b) 1 day
Amoun o bio oil (g)
Solubili y (%)
0
20
40
60
80
100
1 2 3 4 5 6
(c) 3 days
Amoun o bio oil (g)
Solubili y (%)
0
20
40
60
80
100
1 2 3 4 5 6
(e) 7 days
Amoun o bio oil (g)
Solubili y (%)
0
20
40
60
80
100
1 2 3 4 5 6
(d) 5 days
Figu e 3.
The solubili y o he emulsions wi h di e en bio-oil amoun s (B/E = 1) (
a
) 1 h, (
b
) 1 day,
(c) 3 days, (d) 5 days, and (e) 7 days.
Ene gies 2018,11, 3031 8 o 13
Ene gies 2018, 11, x FOR PEER REVIEW 8 o 13
Figu e 4. Fou ie ans o m in a ed spec oscopy (FTIR) spec a o emulsion (2 g bio-oil, B/E = 1) a
h ee egions o (a) 1 h, (b) 1 day, (c) 3 days, (d) 5 days, and (e) 7 days.
3.3. Bio-Oil Solubili y a B/E Ra ios be ween 0.556 and 1
The sepa a ion o he emulsion in he cases o a lowe amoun o bio-oil wi h B/E = 1 was mo e
p onounced compa ed o hose wi h a highe amoun o bio-oil. To s udy he solubili y o he bio-oil,
he solubili y a he B/E a ios o 0.556–1 was in es iga ed. The su ac an ’s concen a ion was one o
he mos impo an ac o s in luencing he solubili y o emulsions. The bio-oil and diesel con en s
Wa enumbe (cm-1)
In ensi y (%T)
1000200030004000
60
65
70
75
80
85
90
95
100
Bo om
Middle
Top
(e) 7 days
Wa enumbe (cm-1)
In ensi y (%T)
1000200030004000
60
65
70
75
80
85
90
95
100
Bo om
Middle
Top
(d) 5 days
Wa enumbe (cm-1)
In ensi y (%T)
1000200030004000
60
65
70
75
80
85
90
95
100
Bo om
Middle
Top
(c) 3 days
Wa enumbe (cm-1)
In ensi y (%T)
1000200030004000
60
65
70
75
80
85
90
95
100
Bo om
Middle
Top
(a) 1 h
Wa enumbe (cm-1)
In ensi y (%T)
1000200030004000
60
65
70
75
80
85
90
95
100
Bo om
Middle
Top
(b) 1 day
Figu e 4.
Fou ie ans o m in a ed spec oscopy (FTIR) spec a o emulsion (2 g bio-oil, B/E = 1) a
h ee egions o (a)1h,(b) 1 day, (c) 3 days, (d) 5 days, and (e) 7 days.
Ene gies 2018,11, 3031 9 o 13
3.3. Bio-Oil Solubili y a B/E Ra ios be ween 0.556 and 1
The sepa a ion o he emulsion in he cases o a lowe amoun o bio-oil wi h B/E = 1 was mo e
p onounced compa ed o hose wi h a highe amoun o bio-oil. To s udy he solubili y o he bio-oil,
he solubili y a he B/E a ios o 0.556–1 was in es iga ed. The su ac an ’s concen a ion was one
o he mos impo an ac o s in luencing he solubili y o emulsions. The bio-oil and diesel con en s
we e ixed a 2 g and 20 g, espec i ely. An inc ease in he amoun o he emulsi ie o a dec ease in he
B/E a io caused mo e bio-oil o dissol e in o he emulsion (Figu e 5). The solubili y a B/E = 1 on
he 7 h day was only 12.02 w %. When he B/E a io dec eased o 0.556, he solubili y inc eased o
57.81 w
%, implying ha a highe emulsi ie concen a ion ende ed a highe solubili y o he bio-oil
in o he emulsion.
The FTIR spec a a h ee egions (i.e., op, middle, and bo om liquid le els in he ube) in he
emulsion wi h 2 g bio-oil and B/E = 1 o 7 days a e displayed in Figu e 4e, showing he s abili y o
he emulsion. The FTIR spec a almos o e lap and coincide wi h each o he , con i ming homogenei y
and highe s abili y o he emulsion.
Ene gies 2018, 11, x FOR PEER REVIEW 9 o 13
we e ixed a 2 g and 20 g, espec i ely. An inc ease in he amoun o he emulsi ie o a dec ease in
he B/E a io caused mo e bio-oil o dissol e in o he emulsion (Figu e 5). The solubili y a B/E = 1 on
he 7 h day was only 12.02 w %. When he B/E a io dec eased o 0.556, he solubili y inc eased o
57.81 w %, implying ha a highe emulsi ie concen a ion ende ed a highe solubili y o he bio-
oil in o he emulsion.
The FTIR spec a a h ee egions (i.e., op, middle, and bo om liquid le els in he ube) in he
emulsion wi h 2 g bio-oil and B/E = 1 o 7 days a e displayed in Figu e 4e, showing he s abili y o
he emulsion. The FTIR spec a almos o e lap and coincide wi h each o he , con i ming
homogenei y and highe s abili y o he emulsion.
Figu e 5. The solubili y o he emulsions wi h di e en B/E a ios (2 g bio-oil) a e 7 days.
3.4. Tempe a u e E ec
The luidi y o he bio-oil was low a oom empe a u e. To inc ease he luidi y o he emulsion
du ing s o age, he emulsion was hea ed a 100 °C in he o en o 7 days. In gene al, bo h he iscosi y
and in e acial ension dec eased wi h inc easing empe a u e, making he emulsi ica ion easie [15].
This esul ed in an inc eased deg ee o solubili y a 100 °C compa ed o ha a oom empe a u e.
Compa ed o he s o age o he emulsion a oom empe a u e, he solubili y in he case o 2 g bio-oil
wi h B/E = 1 a 100 °C p omo ed he solubili y o 59.86 w % om 12.02 w % a oom empe a u e
(Figu e 6). This clea ly indica es ha he e ec o he bio-oil empe a u e a B/E = 1 played an
impo an ole in imp o ing i s solubili y. Howe e , he impac o he s o age empe a u e in he case
o B/E= 0.556 was no o he same magni ude; he solubili y being me ely in ensi ied om 57.81 w %
a oom empe a u e o 63.45 w % a 100 °C, accoun ing o an inc ease o 6.64 w %. O e all, he
empe a u e e ec on he solubili y o bio-oil inc eased when he B/E a io inc eased.
B/E a io
Solubili y (%)
0
20
40
60
80
100
2 g bio oil, 2 g emulsi ie
2 g bio oil, 2.4 g emulsi ie
2 g bio oil, 2.8 g emulsi ie
2 g bio oil, 3.2 g emulsi ie
2 g bio oil, 3.6 g emulsi ie
0.556 0.625 0.714 0.833 1.000
Figu e 5. The solubili y o he emulsions wi h di e en B/E a ios (2 g bio-oil) a e 7 days.
3.4. Tempe a u e E ec
The luidi y o he bio-oil was low a oom empe a u e. To inc ease he luidi y o he emulsion
du ing s o age, he emulsion was hea ed a 100
◦
C in he o en o 7 days. In gene al, bo h he iscosi y
and in e acial ension dec eased wi h inc easing empe a u e, making he emulsi ica ion easie [
15
].
This esul ed in an inc eased deg ee o solubili y a 100
◦
C compa ed o ha a oom empe a u e.
Compa ed o he s o age o he emulsion a oom empe a u e, he solubili y in he case o 2 g bio-oil
wi h B/E = 1 a 100
◦
C p omo ed he solubili y o 59.86 w % om 12.02 w % a oom empe a u e
(Figu e 6). This clea ly indica es ha he e ec o he bio-oil empe a u e a B/E = 1 played an
impo an ole in imp o ing i s solubili y. Howe e , he impac o he s o age empe a u e in he case
o
B/E = 0.556
was no o he same magni ude; he solubili y being me ely in ensi ied om
57.81 w
%
a oom empe a u e o 63.45 w % a 100
◦
C, accoun ing o an inc ease o 6.64 w %. O e all, he
empe a u e e ec on he solubili y o bio-oil inc eased when he B/E a io inc eased.