Biodiesel from rapeseed and sunflower oil: Effect of the transesterification conditions and oxidation stability

Ci a ion: Khan, E.; Ozal in, K.; Spagnuolo, D.; Be nal-Ballen, A.; Piskuno , M.V.; Di Ma ino, A. Biodiesel om Rapeseed and Sun lowe Oil: E ec o he T anses e i ica ion Condi ions and Oxida ion S abili y. Ene gies 2023,16, 657. h ps://doi.o g/10.3390/ en16020657 Academic Edi o : A ilio Con e i Recei ed: 11 No embe 2022 Re ised: 16 Decembe 2022 Accep ed: 27 Decembe 2022 Published: 5 Janua y 2023 Copy igh : © 2023 by he au ho s. Licensee MDPI, Basel, Swi ze land. This a icle is an open access a icle dis ibu ed unde he e ms and condi ions o he C ea i e Commons A ibu ion (CC BY) license (h ps:// c ea i ecommons.o g/licenses/by/ 4.0/). ene gies A icle Biodiesel om Rapeseed and Sun lowe Oil: E ec o he T anses e i ica ion Condi ions and Oxida ion S abili y Elena Khan 1, Kadi Ozal in 2, Damiano Spagnuolo 3, And es Be nal-Ballen 4, Maxim V. Piskuno 5 and An onio Di Ma ino 1,* 1Resea ch School o Chemis y & Applied Biomedical Sciences, Tomsk Poly echnic Uni e si y, Lenin A enue 43, Tomsk 63400, Russia 2Cen e o Polyme Sys ems, Uni e si y Ins i u e, Tomas Ba a Uni e si y in Zlin, Nam. T.G.M. 5555, 76001 Zlin, Czech Republic 3Depa men o Chemical, Biological, Pha maceu ical and En i onmen al Sciences, Uni e si y o Messina, Sali a Spe one 31, 98166 Messina, I aly 4Facul ad de Educación, G upo de in es igacion Conciencia, Uni e sidad An onio Na iño, Calle 22 su No. 12D-81, Bogo a 111821, Colombia 5Hea Mass T ans e Labo a o y, Tomsk Poly echnic Uni e si y, Lenin A enue 43, Tomsk 63400, Russia *Co espondence: [email p o ec ed]u Abs ac : In his s udy, we p oduced biodiesel uel om wo ege al sou ces, apeseed oil and sun lowe oil, by anses e i ica ion eac ion. The s udy aims o e alua e he impac o ype o alcohol, i s concen a ion and he eac ion ime, while keeping cons an he empe a u e and he ca alys on he yield and quali y o he biodiesel. Fo alcohol, me hanol and e hanol we e used a a mola a io wi h he oil om 3 o 24. T anses e i ica ion was pe o med a a ious eac ion imes; 20, 40, 60 and 90 min o each oil and de ined alcohol:oil mola a io. The in luence o hese pa ame e s on he biodiesel yield and p ope ies we e in es iga ed in e ms o densi y, iscosi y, hea ing alue, lash poin , elemen al con en , densi y and oxida i e s abili y o he inal p oduc . The bene i o oxida ion s abilize s, ca echol and 4-allyl-2,6-dime hoxyphenol was in es iga ed. Resul s demons a e ha o apeseed oil, he op imum eac ion condi ions o ob ain a highe yield and quali y o biodiesel we e an alcohol:oil mola a io o 15:1, wi h 60-min eac ion ime a 50 ◦ C; while in he case o sun lowe oil, he bes yield and biodiesel quali y we e a an 18:1 mola a io, wi h a 40-min eac ion ime and a 50 ◦ C. In bo h cases, me hanol p o ides he highes yields o biodiesel, and he ob ained p oduc s sa is y he equi ed s anda ds and p esen a simila i y wi h mine al diesel es ed in same condi ions. Keywo ds: bio uel; apeseed oil; sun lowe oil; anses e i ica ion; ca echol; 4-allyl-2,6-dime hoxyphenol 1. In oduc ion Ene gy ep esen s a key sou ce o economic g ow h, and since hei disco e y, ossil uels ha e been he majo con ibu o o ul illing ene gy needs [ 1 ]. Howe e , due o en i onmen al issues ela ed o he o e use and combus ion o hese uels, oge he wi h he inc ease in p ice and deple ion o na u al ene gy, sou ces ha e o ced esea che s o ind cos -e ec i e, sus ainable, enewable and e icien al e na i e ene gy sou ces [ 2 ]. To da e, se e al enewable sou ces, including wa e , wind, geo he mal and bio uels ha e been explo ed o educe he use o ossil uels, as well as hei en i onmen al impac caused by emissions o g eenhouse gases. Biodiesel is an en i onmen ally iendly ene gy sou ce, due o lowe di ec and indi ec g eenhouse gas emissions compa ed o ossil uels [ 3 ]. The adop ion o biodiesel can de ini ely help o p ese e he ecological balance compa ed o ossil uels. Biodiesel is mainly p oduced by ou app oaches: blending o oils; py olysis ( he mal c acking); mic oemulsion; and anses e i ica ion [ 4 ]. Among hese, anses e i ica ion is conside ed he bes economical echnology, due o he ope a i e condi ions a low p essu e and empe a u e and maximum p oduc yield [5]. Ene gies 2023,16, 657. h ps://doi.o g/10.3390/en16020657 h ps://www.mdpi.com/jou nal/ene gies Ene gies 2023,16, 657 2 o 13 By he anses e i ica ion eac ion, biodiesel is ob ained by mixing alcohol wi h aw ma e ials con aining iglyce ides such as ege able oil, animal a , algae o ecycling cooking oil. In he p esence o a ca alys , he iglyce ides eac wi h alcohol o ming a y acid alkyl es e (biodiesel) as he main componen , and glyce ol, which ep esen s a by-p oduc [ 4 – 7 ]. The anses e i ica ion aims o educe he iscosi y o he ege al oil [ 4 ]. Al hough he p ocedu e is simple om he chemical poin s o iew, i is di icul o conduc i p ope ly, and in addi ion, he ob ained biodiesel mus adhe e o he in e na ional s anda d. The e a e many pa ame e s in he p oduc ion o biodiesel, such as he ype and concen a ion o ca alys , he alcohol and i s mola a io wi h oil, oge he wi h he empe a u e and he eac ion ime [ 8 , 9 ]. Among all o hese, he na u e o alcohol and he mola a io o alcohol:oil a e he a iable, which mos ly a ec he yield and he inal p ope ies o he biodiesel [10]. Among he di e en alcohols used in he anses e i ica ion p ocess, me hanol and e hanol a e a o ed when ege able oils a e used as eed-s ock. Me hanol is gene ally he p ima y choice, due o i s quick and e icien eac ion wi h iglyce ides, and i s mola s uc u e educes he s e ic hind ance, which is esponsible o a low biodiesel yield [ 11 ]. Compa ed o me hanol, e hanol has a highe cos and less eac i i y due o he o ma ion o azeo ope wi h wa e , causing uneasy eco e y [ 12 ]. Howe e , in e es in using e hanol om biological sou ces is g owing, in o de o make he ull p ocess be conside ed as bio-based and enewable, e en i he e hanol eac i i y is s ongly ela ed o he eeds ock and he eac ion condi ions [12,13]. The amoun o alcohol in he anses e i ica ion, exp essed in e ms o he mola a io o alcohol o iglyce ides, is a key a iable ha has a di ec impac on he eac ion yield, quali y and cos o he inal p oduc [ 14 ]. I is well known ha in anses e i ica ion, h ee moles a e o alcohol, h ee moles a e ob ained om a y acids and one om glyce ol. Due o he e e sibili y o he eac ion, he alcohol o iglyce ides mola a io has o be highe compa ed o he s oichiome ic a io, in o de o enhance he miscibili y and he in e ac ion be ween he alcoholic and he oil phase [ 12 ]. Gene ally, he mola a io alls in he ange om 6:1 o 30:1, depending on he ype o oil and alcohol used and i s sou ce [ 15 – 19 ]. De ining he op imal mola a io is highly impo an , as he con en o alcohol in luences he glyce ol solubili y wi hin he es e phase, educing he biodiesel yield due o he shi o he eac ion owa ds he eagen ype [15]. The eac ion ime ep esen s ano he impo an pa ame e o se , as he con e sion a e inc eases g adually o e ime, e en i a p olonged ime dec eases he inal p oduc ion yield due o he e e sibili y o he eac ion. As epo ed in [ 17 ], he eac ion ime alls be ween 20 min and up o se e al hou s, acco ding o he ca alys , olumes and ypes o alcohol and oil used. Gene ally, wi h base ca alys s, he maximum yield is eached wi hin 2 h, while a longe ime is equi ed o acid ca alyze s due o hei lowe eac i i y [20]. Ano he pa ame e o con ol du ing he anses e i ica ion is he empe a u e, as i di ec ly a ec s he eac ion a e; a highe empe a u e and eac ion a e means a highe yield. Howe e , he empe a u e should be lowe han he boiling poin o he alcohol, o a oid i s loss and minimize he soap o ma ion, which has a nega i e impac on he inal yield. Depending on he ype o alcohol, me hanol o e hanol, he eac ion empe a u e is se be ween 50 and 70 ◦C [17,21]. To ob ain an e icien con e sion a e, he anses e i ica ion equi es he use o a ca a- lys ; ei he homogeneous o he e ogeneous acid o base ca alys s a e used. In homogeneous ca alys s, soap o ma ion, co osion o eac o componen s and eco e y issues a e he ecu en d awbacks. Con e sely, he e ogeneous ca alys s a e non-co osi e and en i on- men ally iendly, and can be easily sepa a ed om he p oduc s [ 22 ]. Sodium hyd oxide (NaOH) and po assium hyd oxide (KOH) a e he he e ogeneous ca alys s mos ly adop ed in he anses e i ica ion p ocess om ege al oils [23]. Conside ing wha has been epo ed abo e, he eac ion pa ame e s such as he na u e o he ca alys , ime and empe a u e a e pa ame e s ha can be easily moni o ed in he biodiesel p oduc ion p ocess. Howe e , he alcohol o oil mola a io and he ype o alcohol Ene gies 2023,16, 657 3 o 13 s ill seem o be he majo challenges wi h he anses e i ica ion o ege able oil, despi e he many s udies ha ha e been epo ed. Thei op imiza ion is ela i ely complica ed, due o hei impac on he pe o mance o he p oduced biodiesel as uel. The e o e, o es ablish he op imal eac ion, we se up condi ions ha can be easily applied o he la ge-scale p oduc ion o biodiesel. The aim o he p esen ed expe imen al wo k is o e alua e and ind ou he con enien ope a ion condi ions in he anses e i ica ion o apeseed and sun lowe oil, and hei in luence on he ob ained biodiesel p ope ies. In pa icula , he in e es is o de ine he di e ences be ween me hanol and e hanol, he mola a io he alcohol o oil and he eac ion ime, keeping he ca alys ype, i s concen a ion and he empe a u e cons an . The in luence o a ia ion in hose pa ame e s on he biodiesel yield and quali y is he goal o he wo k. Oxida ion s abili y and he e ec o wo oxida ion s abilize s, 4-allyl-2,6-dime hoxyphenol and ca echol, we e also in es iga ed. 2. Ma e ials and Me hods 2.1. Ma e ials Fo he biodiesel p oduc ion, e ined apeseed oil and sun lowe oil we e p o ided by local p oduce s. The eagen s used o he anses e i ica ion and pu i ica ion s eps we e as ollows: me hanol (99.9%); and po assium hyd oxide (95%). Fo doping he wo biodiesels, wo an ioxidan s we e used: ca echol (>99% CAS 120-80-9); and 4-ally-2,6-dime hoxyphenol (90% CAS 6627-88-9). These we e pu chased om Sigma–Ald ich (Moscow, Russia). 2.2. Biodiesel P epa a ion The biodiesel om apeseed oil and sun lowe oil was ob ained by anses e i ica ion eac ion using homogeneous ca alys s, as i ep esen s a con enien and well-known app oach. In b ie , 200 g o each oil was p ehea ed a 120 ◦ C o 30 min unde s i ing o emo e he mois u e, and hen ans e ed o a 500 mL glass lask. A e wa ds, he solu ion con aining alcohol (me hanol o e hanol) and he ca alys (KOH) was p epa ed. Fo 5 0 m L o alcohol, 2 g o ca alys was used. The ob ained me hoxide/e hoxide solu ion was pou ed on o he oil, and he eac ion was le o un a 50 ◦ C o an es ablished ime. The alcohol concen a ion ep esen s one o he a iables e alua ed. Samples a he ollowing alcohol:oil mola a io we e p epa ed: 3:1, 6:1, 9:1, 12:1, 15:1; 18:1, 21:1 and 24:1 o bo h oils used. The second a iable was he eac ion ime, whe ein 4 in e als we e e alua ed: 20 min; 40 min; 60 min; and 90 min. The pa ame e s kep cons an o each expe imen we e he KOH con en (2 g o each 50 mL o alcohol); he empe a u e (50 ◦C); and s i ing speed (700 pm). A e he comple ion o he eac ion, he wo phases we e le o sepa a e by g a i y, and he biodiesel sepa a ed om he glyce ol, washed one ime wi h aqueous ace ic acid solu ion (1% / ) and h ee imes wi h dis illed wa e o emo e un eac ed ca alys s, soap and o he side p oduc s. A e he las washing wi h dis illed wa e , he biodiesel was kep a 120 ◦C o 30 min o emo e he esidual mois u e. The impac o he eac ion ime and he alcohol:oil mola a io on he biodiesel yield was calcula ed using he ollowing equa ion Y(g) = mb mo(1) whe e Y ep esen s he yield (g), while m b and m o he mass (g) o biodiesel and oil, espec i ely. The p epa a ion scheme is epo ed in Figu e 1. Ene gies 2023,16, 657 4 o 13 Ene gies 2023, 16, x FOR PEER REVIEW 4 o 13 whe e Y ep esen s he yield (g), while mb and mo he mass (g) o biodiesel and oil, e- spec i ely. The p epa a ion scheme is epo ed in Figu e 1. Figu e 1. Schema ic illus a ion o he biodiesel p oduc ion p ocess by anses e i ica ion and he pa ame e s o he p ocess and biodiesel cha ac e iza ion. KOH (po assium oxide); R-OH (alcohol). 2.3. Cha ac e iza ion and Quali y E alua ion The impac o he eac ion ime, ype o alcohol and mola a io (alcohol:oil) on he ollowing inal p oduc yield, kinema ic iscosi y, calo i ic alue, lash poin , elemen al analysis, densi y and oxida ion s abili y, we e in es iga ed. 2.3.1. Kinema ic Viscosi y The dynamic iscosi y was de e mined by An on-Paa MCR 502 a 40 °C. Th ee shea a es we e used, speci ically 7.5 s−1; 15 s−1 and 37 s−1 ollowing he ATSM D445 s anda d. Each measu emen was pe o med in iplica e. F om he dynamic iscosi y, he kinema ic iscosi y was calcula ed by he ollowing equa ion 𝑣=ƞ 𝜌 (2) whe e 𝑣, ƞ, 𝜌, a e he kinema ic iscosi y (m2/s), he luid densi y (Kg/m3) and he dy- namic iscosi y (Pa·s), espec i ely. 2.3.2. The Highe Hea ing Value Measu emen The Highe Hea ing Value (HHV) was measu ed by oxygen bomb calo ime e ol- lowing he ASTMD240-14 s anda d. The calo ime e was calib a ed using benzoic acid a 20 °C [24]. 2.3.3. Flash Poin The lash poin , is an indica o o he emaining me hanol and he capaci ies o handling, s o age and sa e y [25]. The Eu opea S anda d (EN 14214) se s he lash poin a 101 °C and he Ame ican S anda d Tes ing Ma e ials ASTM D6751-09 a 93 °C. The lash poin was measu ed wi h a Pensky–Ma ens closed-cup appa a us using pu e biodiesel and biodiesel in a blend wi h diesel. 2.3.4. Densi y The biodiesel densi y in luences he pe o mance o pumps in uel sys ems. The biodiesel densi y was measu ed ollowing he EN ISO (In e na ional O ganiza ion o S anda diza ion) 12185 es me hod. The EN 14214 se s he densi y a 15 °C a 900 kg/m3. Figu e 1. Schema ic illus a ion o he biodiesel p oduc ion p ocess by anses e i ica ion and he pa ame e s o he p ocess and biodiesel cha ac e iza ion. KOH (po assium oxide); R-OH (alcohol). 2.3. Cha ac e iza ion and Quali y E alua ion The impac o he eac ion ime, ype o alcohol and mola a io (alcohol:oil) on he ollowing inal p oduc yield, kinema ic iscosi y, calo i ic alue, lash poin , elemen al analysis, densi y and oxida ion s abili y, we e in es iga ed. 2.3.1. Kinema ic Viscosi y The dynamic iscosi y was de e mined by An on-Paa MCR 502 a 40 ◦ C. Th ee shea a es we e used, speci ically 7.5 s −1 ; 15 s −1 and 37 s −1 ollowing he ATSM D445 s anda d. Each measu emen was pe o med in iplica e. F om he dynamic iscosi y, he kinema ic iscosi y was calcula ed by he ollow- ing equa ion =η ρ(2) whe e , η , ρ , a e he kinema ic iscosi y (m 2 /s), he luid densi y (Kg/m 3 ) and he dynamic iscosi y (Pa·s), espec i ely. 2.3.2. The Highe Hea ing Value Measu emen The Highe Hea ing Value (HHV) was measu ed by oxygen bomb calo ime e ol- lowing he ASTMD240-14 s anda d. The calo ime e was calib a ed using benzoic acid a 20 ◦C [24]. 2.3.3. Flash Poin The lash poin , is an indica o o he emaining me hanol and he capaci ies o han- dling, s o age and sa e y [ 25 ]. The Eu opea S anda d (EN 14214) se s he lash poin a 101 ◦ C and he Ame ican S anda d Tes ing Ma e ials ASTM D6751-09 a 93 ◦ C. The lash poin was measu ed wi h a Pensky–Ma ens closed-cup appa a us using pu e biodiesel and biodiesel in a blend wi h diesel. 2.3.4. Densi y The biodiesel densi y in luences he pe o mance o pumps in uel sys ems. The biodiesel densi y was measu ed ollowing he EN ISO (In e na ional O ganiza ion o S anda diza ion) 12185 es me hod. The EN 14214 se s he densi y a 15 ◦C a 900 kg/m3. 2.3.5. Elemen al Analysis The con en in ca bon, hyd ogen, ni ogen, sul u and oxygen in apeseed and sun lowe biodiesel and diesel uel has been measu ed by The mo Scien i ic Flash 200 0 C HNS /O, G e many. Ene gies 2023,16, 657 5 o 13 2.3.6. Fa y F ee Acid Composi ion o Rapeseed and Sun lowe Biodiesel Fa y ee me hyl acid composi ion in apeseed and sun lowe biodiesel has been e alua ed by gas ch oma og aphy using an FID de ec o . The samples we e collec ed om he sepa a ion unnel (see Figu e 1), and p io o being analyzed, we e washed wi h wa e con aining 1% ace ic acid and dis illed wa e o neu alized un eac ed esidues o ca alys s, emo ing side p oduc s. The ollowing se up has been used: capilla y column 30 ×0.31 ×0.25 ; helium as gas ca ie , low a e o 1 mL/min; empe a u e injec ion 2 80 ◦C ; empe a u e de ec o 300 ◦C; and empe a u e amp 10 ◦C /min s a ing om 220 ◦C. The o al FAME was calcula ed e e ing o he o al mass o he biodiesel using he ollowing equa ion FAME (%) = ∑m b×100 whe e FAME ep esen s he o al mass o he a y acid me hyl es e in pe cen age; he mass o each a y acid (g) and b he o al biodiesel mass (g). The o al con en o FAME was compa ed o he EN 14214 s anda d. The measu emen s we e pe o med in iplica e (Table 1). Table 1. To al FAME and composi ion o apeseed and sun lowe biodiesel. The a e age alue wi h S.D. is epo ed (n= 3). Rapeseed Biodiesel Sun lowe Biodiesel EN 14214 FAME (%) 90.9 (±1.4) 95.5 (±1.9) 96.5 Oleic (18:1) 61.2 (±0.4) 29.4 (±0.3) Linoleic (18:2) 19.7 (±0.6) 58.3 (±1.1) Linolenic (18:3) 5.1 (±0.1) 0.8 (±0.3) Palmi ic (16: 0) 3.3 (±0.1) 4.9 (±0.1) S ea ic (18:0) 0.9 (±0.1) 1.4 (±0.1) o he s 0.7 (±0.1) 0.6 (±0.1) 2.3.7. Oxida ion S abili y The oxida ion s abili y was measu ed by Pe oOXY (Pe o es ) ollowing he p ocedu e desc ibed elsewhe e [ 26 ]. In b ie , 5 cm 3 o he sample was placed in he eac ion essel p essu ized wi h oxygen a 700 kPa, and hea ed o 140 ◦ C. Du ing he oxida ion, oxygen is consumed wi h a subsequen d op in he p essu e d op. The a ia ion in he p essu e is eco ded e e y second. The elapsed ime om he s a o he b eakpoin is he induc ion pe iod a he es empe a u e o 140 ◦C. To enhance he oxida ion s abili y o he p oduced biodiesel, wo s abilize s ha e been es ed: 4-allyl-2,6-dime hoxyphenol; and ca echol. The e ec o he ype o s abilize and he concen a ion (0.05, 0.1 and 0.3% m/m) on he oil s abili y we e in es iga ed. 3. Resul s and Discussion 3.1. E ec o he Alcohol Type and Mola Ra io on he T anses e i ica ion Yield In his s udy, he biodiesel uels we e ob ained by anses e i ica ion o e ined ape- seed and sun lowe oils using KOH as a ca alys in me hanol o e hanol. The e ec o alcohol o mola a io and he na u e o alcohol on he biodiesel yield a e esumed in Figu e 2. As can be seen, he yield o biodiesel inc eases wi h he inc ease in he con- cen a ion o alcohol, and he highes yield was obse ed a mola a io o 15:1 and 18:1 o bo h alcohols, in apeseed and sun lowe oil, espec i ely. Fu he inc emen s in he concen a ion o alcohol led o a dec ease in he biodiesel’s yield om bo h oil sou ces, and pa icula ly using me hanol. Ene gies 2023,16, 657 6 o 13 Ene gies 2023, 16, x FOR PEER REVIEW 7 o 13 Figu e 2. Co ela ion be ween he biodiesel yield (g) and he mola a io o alcohol:oil. (A,B) ape- seed oil; and (C,D) sun lowe oil. Da a a e epo ed as he a e age ± SD (n = 3). 3.2. Densi y The biodiesel densi y p o ides p edic ion o engine ou pu powe and uel con- sump ion [32,33]. I is gene ally highe han in ossil uels, and depends on he composi- ion in a y acids and he pu i y o he eeds ock. Fo apeseed biodiesel, densi y a 15 °C alls in he ange o 0.876–0.891 g/cm3 a he op imal p epa a ion condi ion (me ha- nol/e hanol o oil mola a io o 15:1, eac ion ime o 60 min a 50 °C), while o ha o sun lowe oil a he same empe a u e was in he 0.851–0.883 g/cm3 ange (me ha- nol/e hanol o oil mola a io o 18:1, eac ion ime o 40 min a 50 °C). Conside ing his, he accep able ange o he s anda d EN 14214, in which i is epo ed a 15 °C, is 0.860– 0.900 gm/cm3. 3.3. Kinema ic Viscosi y Viscosi y is an impo an p ope y o iden i y and con ol, as i a ec s he engine s a p ope ies and uel injec ion sys em pe o mance. The uel-ai mix a ec s he pe - o mance o he uel bu ning p ocess in a diesel engine. The quali y o his mix u e de- pends on he luidi y o he uel, which is di ec ly linked o he iscosi y. The kinema ic iscosi y a 40 °C is he pa ame e equi ed by he biodiesel and oil diesel s anda d. In Figu e 3, he kinema ic iscosi y alues o apeseed and sun lowe p oduced, ob ained a di e en alcohol le els:mola oil le els a di e en pe cen age le els, a e shown. F om Figu e 3, he alues o kinema ic iscosi y dec ease when he mola a io inc eases, eaching he minimum a a mola a io o 15:1, and hen sligh ly ises. Such a end is obse able a all es ed shea a es. The lowes kinema ic iscosi y alues ha e been ob- se ed a sha e a e o 15·s−1 a a mola a io o 15:1. A simila end is obse ed in sun- lowe biodiesel, whe e he lowes kinema ic iscosi y is obse ed a alcohol:oil mola a ios o 12:1 (me hanol) and 15:1 (e hanol), and a shea a e o 15 s−1. The la ge di e ences be ween he iscosi y o apeseed and sun lowe oil and he espec i e biodiesel is due o he con e sion o la ge and b anched iglyce ide molecules in o a ligh e linea chain o me hyl o e hyl es e molecules. This inding shows ha he ans-es e i ica ion p ocess has conside ably imp o ed he iscosi y p ope y o apeseed Figu e 2. Co ela ion be ween he biodiesel yield (g) and he mola a io o alcohol:oil. ( A , B ) apeseed oil; and (C,D) sun lowe oil. Da a a e epo ed as he a e age ±SD (n= 3). As epo ed in [ 27 – 29 ], he ela ion be ween he eac ion’s yield and he alcohol o oil mola a io is due o he ac ha a mola a ios lowe han 15:1 ( apeseed oil) and 18:1 (sun lowe oil), he anses e i ica ion was s ill incomple e. As a esul , ising alcohol concen a ion enhances he in e ac ions be ween alcohol molecules and iglyce ides due o an inc ease in miscibili y, mo ing he eac ion owa d comple ion. A mola a ios highe han 15:1 ( apeseed oil) and 18:1 (sun lowe oil), he yield dec eases, as he high alcohol concen a ion leads o an inc ease in glyce ol solubili y. The inc ease o he co-p oduc solubili y le i emain in he biodiesel phase shi in he eac ion equilib ium o he le , and consequen ly lowe s he biodiesel yield. I was obse ed ei he wi h me hanol o e hanol, and in bo h ypes o ege able oils. Conside ing he anses e i ica ion condi ions es ed in he p esen s udy, me hanol was mo e eac i e wi h apeseed and sun lowe oils compa ed o e hanol, as i (me hanol) eac s quickly wi h iglyce ides due o i s sho -chain mola size a oiding he s e ic hind ance e ec s and wa e abso p ion om a mosphe e du ing anses e i ica ion, which di ec ly a ec he inal yield [28]. Beside he impac o he alcohol: oil mola a io on he eac ion yield, he e ec o he eac ion ime and empe a u e ha e been conside ed (Figu e 2). The empe a u e in luences he eac ion a e and he o ma ion o me hyl es e s (me hanol) o e hyl es e s (e hanol). In addi ion, he eac ion was ca ied ou a (50 ◦ C) and a a mosphe ic p essu e, o educe he e apo a ion o he alcohols. As epo ed in [ 30 , 31 ], a highe empe a u es, an ad e se e ec could occu . As can be seen in Figu e 2, o apeseed biodiesel, using me hanol, he yield ends o inc ease, wi h he eac ion ime eaching he maximum a 60 min, ollowed by a dec ease, while using e hanol, he maximum yield is eached a e 60 min, and hen ends o be s able. In sun lowe biodiesel, he maximum yields a e sligh ly shi ed; using me hanol, i inc eases up o 40 min and hen dec eases, while using e hanol, he maximum yield is eached a e 90 min o eac ion. The educ ion in he yield when he eac ion ime is p olonged is p obably due o he o ma ion o soaps. As illus a ed in Figu e 2, he di e ence in yield is obse able depending on he oil eeds ock and he alcohol used. Using me hanol, he e is a dec ease in he yield when eac ion ime is p olonged, while wi h e hanol i is s able, indica ing a p obable highe o ma ion o soaps when me hanol is used. Ene gies 2023,16, 657 7 o 13 3.2. Densi y The biodiesel densi y p o ides p edic ion o engine ou pu powe and uel consump- ion [ 32 , 33 ]. I is gene ally highe han in ossil uels, and depends on he composi ion in a y acids and he pu i y o he eeds ock. Fo apeseed biodiesel, densi y a 15 ◦ C alls in he ange o 0.876–0.891 g/cm 3 a he op imal p epa a ion condi ion (me hanol/e hanol o oil mola a io o 15:1, eac ion ime o 60 min a 50 ◦ C), while o ha o sun lowe oil a he same empe a u e was in he 0.851–0.883 g/cm 3 ange (me hanol/e hanol o oil mola a io o 18:1, eac ion ime o 40 min a 50 ◦ C). Conside ing his, he accep able ange o he s anda d EN 14214, in which i is epo ed a 15 ◦C, is 0.860–0.900 gm/cm3. 3.3. Kinema ic Viscosi y Viscosi y is an impo an p ope y o iden i y and con ol, as i a ec s he engine s a p ope ies and uel injec ion sys em pe o mance. The uel-ai mix a ec s he pe o mance o he uel bu ning p ocess in a diesel engine. The quali y o his mix u e depends on he luidi y o he uel, which is di ec ly linked o he iscosi y. The kinema ic iscosi y a 40 ◦ C is he pa ame e equi ed by he biodiesel and oil diesel s anda d. In Figu e 3, he kinema ic iscosi y alues o apeseed and sun lowe p oduced, ob ained a di e en alcohol le els:mola oil le els a di e en pe cen age le els, a e shown. F om Figu e 3, he alues o kinema ic iscosi y dec ease when he mola a io inc eases, eaching he minimum a a mola a io o 15:1, and hen sligh ly ises. Such a end is obse able a all es ed shea a es. The lowes kinema ic iscosi y alues ha e been obse ed a sha e a e o 15 · s −1 a a mola a io o 15:1. A simila end is obse ed in sun lowe biodiesel, whe e he lowes kinema ic iscosi y is obse ed a alcohol:oil mola a ios o 12:1 (me hanol) and 15:1 (e hanol), and a shea a e o 15 s−1. Ene gies 2023, 16, x FOR PEER REVIEW 8 o 13 and sun lowe oil, eaching a alue compa able o ha o mine al diesel. This iscosi y di e en ial can be used o con ol biodiesel p oduc ion h ough anses e i ica ion [34]. Figu e 3. Kinema ic - iscosi y (40 °C, mm2/s2) o apeseed biodiesel ob ained using me hanol (A) and e hanol (B), and sun lowe biodiesel ob ained using me hanol (C) and e hanol (D) a a di e en alcohol o oil mola a io. Da a a e epo ed as he a e age ± SD (n = 3). 3.4. Highe Hea ing Value (HHV) The highe hea ing alue (HHV) is de ined as a he mal ene gy eleased by he combus ion o a uni quan i y o uel, and hence cha ac e izes he ene gy con en o he uel [35,36]. HHV measu emen s o colza and sun lowe biodiesel ob ained wi h me h- anol and e hanol a di e en mola a ios a e gi en in Figu e 4. The HHV o he biodiesel samples is ela i ely high, anging in he case o apeseed biodiesel om 39.24 o 41.18 MJ/kg and om 38.58 o 41.07 MJ/Kg ob ained using me hanol and e hanol, espec i ely. In biodiesel om sun lowe , he alues ange om 36.92 o 40.69 MJ/Kg (me hanol) and 38.92 and 39.60 MJ/Kg (e hanol). Al hough hese alues all wi hin he equi ed s and- a ds, hey a e sligh ly lowe compa ed o ossil diesel. This esul can be explained by he p esence o oxygen in he biodiesel, as well as by he low pe cen age o ca bon and hy- d ogen compa ed o ossil diesel (see Table 2 elemen al analysis). I can be emphasized ha da a a e e y spa e because o no egula inc ease o dec ease endency when he mola a io is inc eased. The apeseed biodiesel has i s maximum hea ing alue a 15:1 (using me hanol) and 21:1 (using e hanol), while sun lowe biodiesel shows he highes HHV a 18:1 (using me hanol) and 24:1 (using e hanol). Table 2. Elemen al analysis o SB (biodiesel om sun lowe oil); RB (biodiesel om apeseed oil) and diesel. Bo h we e ob ained using me hanol. Measu emen s we e pe o med in iplica e, and he a e age alue is epo ed. S.D. less han 5% (n = 3). Elemen SB RB Diesel C 80.3 79.9 86.6 H 10.5 10.3 13.4 O 8.1 8.5 - N 1.1 1.3 - C/H 7.6 7.7 6.46 Figu e 3. Kinema ic - iscosi y (40 ◦ C, mm 2 /s 2 ) o apeseed biodiesel ob ained using me hanol ( A) a nd e hanol ( B ), and sun lowe biodiesel ob ained using me hanol ( C ) and e hanol ( D ) a a di e en alcohol o oil mola a io. Da a a e epo ed as he a e age ±SD (n= 3). The la ge di e ences be ween he iscosi y o apeseed and sun lowe oil and he espec i e biodiesel is due o he con e sion o la ge and b anched iglyce ide molecules in o a ligh e linea chain o me hyl o e hyl es e molecules. This inding shows ha he ans-es e i ica ion p ocess has conside ably imp o ed he iscosi y p ope y o apeseed and sun lowe oil, eaching a alue compa able o ha o mine al diesel. This iscosi y di e en ial can be used o con ol biodiesel p oduc ion h ough anses e i ica ion [34]. Ene gies 2023,16, 657 8 o 13 3.4. Highe Hea ing Value (HHV) The highe hea ing alue (HHV) is de ined as a he mal ene gy eleased by he combus ion o a uni quan i y o uel, and hence cha ac e izes he ene gy con en o he uel [ 35 , 36 ]. HHV measu emen s o colza and sun lowe biodiesel ob ained wi h me hanol and e hanol a di e en mola a ios a e gi en in Figu e 4. The HHV o he biodiesel samples is ela i ely high, anging in he case o apeseed biodiesel om 39.24 o 41.18 MJ/kg and om 38.58 o 41.07 MJ/Kg ob ained using me hanol and e hanol, espec i ely. In biodiesel om sun lowe , he alues ange om 36.92 o 40.69 MJ/Kg (me hanol) and 38.92 and 39.60 MJ/Kg (e hanol). Al hough hese alues all wi hin he equi ed s anda ds, hey a e sligh ly lowe compa ed o ossil diesel. This esul can be explained by he p esence o oxygen in he biodiesel, as well as by he low pe cen age o ca bon and hyd ogen compa ed o ossil diesel (see Table 2elemen al analysis). I can be emphasized ha da a a e e y spa e because o no egula inc ease o dec ease endency when he mola a io is inc eased. The apeseed biodiesel has i s maximum hea ing alue a 15:1 (using me hanol) and 21:1 (using e hanol), while sun lowe biodiesel shows he highes HHV a 18:1 (using me hanol) and 24:1 (using e hanol). Ene gies 2023, 16, x FOR PEER REVIEW 9 o 13 Figu e 4. HHV o biodiesel ob ained a a ious alcohol: oil mola a io. (A) apeseed biodiesel and (B) sun lowe biodiesel. Da a a e epo ed as he a e age ± SD (n = 3). 3.5. Flash Poin The lash poin is he lowes empe a u e a which a uel eleases a su icien con- cen a ion o apo s ha ha e mixed wi h ai and become in lamed [25]. The lash poin empe a u e indica es he o e all lammabili y haza d in he p esence o ai ; a highe lash poin makes bio-diesel sa e o handling and s o ing, and o his eason, knowing he lash poin is undamen al o e e y ype o biodiesel in o de o classi y i as non- haza dous unde he i e egula ions. Compa ed o diesel, biodiesel has a highe lash poin due o he p esence o a y acid me hyl es e s (FAMEs) o a y acid e hyl es e s (FAEEs), which a e no ola ile. As he lash poin a ies in e sely wi h he uel’s ola- ili y, biodiesel is sa e o handle a a highe empe a u e han ossil diesel. The lashpoin o he apeseed (RB) and sun lowe (SB) biodiesel pu e and in he blend wi h diesel was e alua ed, and he esul s a e esumed in Figu e 5. The bio- diesel—diesel blends we e p epa ed by mixing he wo componen s a a di e en weigh a io. The biodiesels used o he lash poin cha ac e iza ion we e: (1) om apeseed oil, biodiesel ob ained a alcohol: oil mola a io o 15:1, 60 min eac ion ime a 50 °C; and (2) om sun lowe ha ob ained a 18:1 mola a io; 40 min eac ion ime and 50 °C. The lash poin alues can a y acco ding o he sou ce and he quali y o he oil [37]. Figu e 4. HHV o biodiesel ob ained a a ious alcohol: oil mola a io. ( A ) apeseed biodiesel and (B) sun lowe biodiesel. Da a a e epo ed as he a e age ±SD (n= 3). Table 2. Elemen al analysis o SB (biodiesel om sun lowe oil); RB (biodiesel om apeseed oil) and diesel. Bo h we e ob ained using me hanol. Measu emen s we e pe o med in iplica e, and he a e age alue is epo ed. S.D. less han 5% (n= 3). Elemen SB RB Diesel C 80.3 79.9 86.6 H 10.5 10.3 13.4 O 8.1 8.5 - N 1.1 1.3 - C/H 7.6 7.7 6.46 3.5. Flash Poin The lash poin is he lowes empe a u e a which a uel eleases a su icien con- cen a ion o apo s ha ha e mixed wi h ai and become in lamed [ 25 ]. The lash poin empe a u e indica es he o e all lammabili y haza d in he p esence o ai ; a highe lash poin makes bio-diesel sa e o handling and s o ing, and o his eason, knowing he lash poin is undamen al o e e y ype o biodiesel in o de o classi y i as nonhaza dous unde he i e egula ions. Compa ed o diesel, biodiesel has a highe lash poin due o he p esence o a y acid me hyl es e s (FAMEs) o a y acid e hyl es e s (FAEEs), which a e no ola ile. As he lash poin a ies in e sely wi h he uel’s ola ili y, biodiesel is sa e o handle a a highe empe a u e han ossil diesel. Ene gies 2023,16, 657 9 o 13 The lashpoin o he apeseed (RB) and sun lowe (SB) biodiesel pu e and in he blend wi h diesel was e alua ed, and he esul s a e esumed in Figu e 5. The biodiesel—diesel blends we e p epa ed by mixing he wo componen s a a di e en weigh a io. Ene gies 2023, 16, x FOR PEER REVIEW 9 o 13 Figu e 4. HHV o biodiesel ob ained a a ious alcohol: oil mola a io. (A) apeseed biodiesel and (B) sun lowe biodiesel. Da a a e epo ed as he a e age ± SD (n = 3). 3.5. Flash Poin The lash poin is he lowes empe a u e a which a uel eleases a su icien con- cen a ion o apo s ha ha e mixed wi h ai and become in lamed [25]. The lash poin empe a u e indica es he o e all lammabili y haza d in he p esence o ai ; a highe lash poin makes bio-diesel sa e o handling and s o ing, and o his eason, knowing he lash poin is undamen al o e e y ype o biodiesel in o de o classi y i as non- haza dous unde he i e egula ions. Compa ed o diesel, biodiesel has a highe lash poin due o he p esence o a y acid me hyl es e s (FAMEs) o a y acid e hyl es e s (FAEEs), which a e no ola ile. As he lash poin a ies in e sely wi h he uel’s ola- ili y, biodiesel is sa e o handle a a highe empe a u e han ossil diesel. The lashpoin o he apeseed (RB) and sun lowe (SB) biodiesel pu e and in he blend wi h diesel was e alua ed, and he esul s a e esumed in Figu e 5. The bio- diesel—diesel blends we e p epa ed by mixing he wo componen s a a di e en weigh a io. The biodiesels used o he lash poin cha ac e iza ion we e: (1) om apeseed oil, biodiesel ob ained a alcohol: oil mola a io o 15:1, 60 min eac ion ime a 50 °C; and (2) om sun lowe ha ob ained a 18:1 mola a io; 40 min eac ion ime and 50 °C. The lash poin alues can a y acco ding o he sou ce and he quali y o he oil [37]. Figu e 5. Rela ionship be ween lash poin ( ◦ C) and biodiesel con en in he biodiesel-diesel mix u e. SB = sun lowe biodiesel; RB = apeseed biodiesel. Bo h we e ob ained using me hanol a he op imal mola a io, as desc ibed in he p e ious sec ions. The biodiesels used o he lash poin cha ac e iza ion we e: (1) om apeseed oil, biodiesel ob ained a alcohol: oil mola a io o 15:1, 60 min eac ion ime a 50 ◦ C; and (2) om sun lowe ha ob ained a 18:1 mola a io; 40 min eac ion ime and 50 ◦C. The lash poin alues can a y acco ding o he sou ce and he quali y o he oil [ 37 ]. The ends in Figu e 5show ha he highes lashpoin o pu e BS and RB a e simila wi hou a s a is ical di e ence. In he case o biodiesel-diesel blends, as expec ed and epo ed in se e al published wo ks [ 38 ], inc easing he pe cen age o diesel in he blend biodiesel-diesel causes he lash poin empe a u e dec ease, eaching he lowes alue a a ound 80 ◦ C o SB and RB (10% biodiesel–90% diesel) (This is due o he ac ha diesel has a lowe lashpoin compa ed o biodiesel, and hus he esul ing blend (diesel-biodiesel) has a lowe lashpoin han he pu e biodiesel. The educ ion in he lashpoin alue is p opo ional o he pe cen age o diesel in he blend. As a gene al conclusion, no s a is ical di e ences ha e been obse ed in he SB and RB lash poin s. biodiesel con en as he ends o e lap. 3.6. Elemen al Analysis o Biodiesels and Diesel In Table 3, he C, H, O, N con en in biodiesel om sun lowe oil (SB) and apeseed oil (RB) a e epo ed and compa ed o he ossil uel diesel. The elemen al analysis demons a es no signi ican di e ence in he C, H, O, N con en be ween SB and RB. Compa ed o diesel, howe e , he C and H con en in SB and RB is sligh ly lowe , as also demons a ed in p e ious s udies [ 39 , 40 ], wi h a consequen inc ease in he C/H a io. One key di e ence be ween biodiesel uels and pe oleum diesel is he high con en o oxygen, which imp o es combus ion and pe o mance cha ac e is ics. Biodiesel has a small ni ogen con en , which esul s in highe emissions o NOx.