Production of Biodiesel from Candlenut Oil Using a Two-Step Co

Production of Biodiesel from Candlenut Oil Using a Two-step Co-solvent Method and Evaluation of Its Gaseous Emissions Lan Ngoc Pham1, Boi Van Luu1, Hung Duong Phuoc2, Hanh Ngoc Thi Le3, Hoa Thi Truong4, Phuong Duc Luu1, Masakazu Furuta3, Kiyoshi Imamura5＊ and Yasuaki Maeda5 1 Faculty of Chemistry, VNU University of Science, Hanoi, 19 Le Thanh Tong, Hoan Kiem District, Hanoi, VIETNAM 2 Ministry of Natural Resources and Environment, 10 Ton That Thuyet Str., Hanoi, 100000, VIETNAM 3 Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-Ku, Sakai, Osaka 599-8531, JAPAN 4 Danang Environmental Technology Center, Institute of Environmental Technology, Vietnam Academy of Science and Technology, Tran Dai Nghia Road, Ngu Hanh Son Dist., Danang city 59000, VIETNAM 5 Research Institute of University-Community Collaborations, Osaka Prefecture University, 1-2 Gakuen-cho, Naka-Ku, Sakai, Osaka 599-8531, JAPAN

Abstract: Candlenut oil (CNO) is a potentially new feedstock for biodiesel (BDF) production. In this paper, a two-step co-solvent method for BDF production from CNO was examined. Firstly, esterification of free fatty acids (FFAs) (7 wt%) present in CNO was carried out using a co-solvent of acetonitrile (30 wt%) and

H2SO4 as a catalyst. The content of FFAs was reduced to 0.8 wt% in 1 h at 65℃. Subsequent transesterification of the crude oil produced was carried out using a co-solvent of acetone (20 wt%) and 1 wt% potassium hydroxide (KOH). Ester content of 99.3% was obtained at 40℃ in 45 min. The water content in BDF was 0.023% upon purification using vacuum distillation at 5 kPa. The components of CNO BDF were characterized using a Fourier-transform infrared spectrometry and gas chromatography-flame ionization detector. The physicochemical properties of BDF satisfied the ASTM D6751-02 standard. The gaseous exhaust emissions from the diesel engine upon combustion of the BDF blends (B0–B100) with petro- diesel were examined. The emissions of carbon monoxide and hydrocarbons were clearly lower, but that of nitrogen oxides was higher in comparison to those from petro-diesel.

Key words: candlenut oil, biodiesel, co-solvent technology, transesterification, exhaust gases

1 INTRODUCTION BDF, or fatty acid methyl ester（FAME）, is produced by Currently, biofuels are garnering particular interest. transesterification of triglycerides of vegetable oils or There are two main reasons for this. Firstly, fossil fuels animal fats. One of the disadvantages of BDF is its relative- which are being over-exploited have limited reserves and ly high price, which is not competitive with petro-diesel3）. thus, will be exhausted in the near future. Secondly, fossil Scientists have been interested in the use of non-edible oils fuels are deemed to have serious side effects on ecosystem as feedstocks to produce BDF, because these oils have rela- and human health because of their greenhouse gas（GHG） tively low cost, and therefore can lower the BDF price. emissions. Increasing concentration of GHGs causes global Non-edible oils such as rubber seed oil, Jatropha seed oil, warming, thereby leading to dramatic and unpredictable Tung oil, castor oil, candlenut oil（CNO）and others may be climate changes1）. In this context, biofuels, including bio- used for BDF production4－6）. diesel fuel（BDF）, being renewable and emitting fewer There have been many investigations on BDF production toxic gases than conventional petro-diesel upon combus- technology. The co-solvent method is a new technology, in tion in an engine, are viewed as promising fuel sources to which a solvent is used for homogenizing reaction systems, replace fossil fuels petro-diesel2）. and shows a lot of advantages compared to the convention-

＊Correspondence to: Kiyoshi Imamura, Research Institute of University-Community Collaborations, Osaka Prefecture University, 1-2 Gakuen-cho, Naka-Ku, Sakai, Osaka 599-8531, JAPAN E-mail: [email protected] Accepted January 9, 2018 (received for review October 13, 2017) Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://www.jstage.jst.go.jp/browse/jos/ http://mc.manusriptcentral.com/jjocs

617 L. N. Pham, B. V. Luu, H. D. Phuoc et al.

al non-co-solvent method. We have developed a method on blends ranging from B0（biodiesel content 0％）to B30 using acetone as a co-solvent for the transesterification of （biodiesel content 30％）petro-diesel12）. plant seed oils to produce BDF6）. The presence of acetone This paper presents the results of BDF production from increases the mutual solubility of methanol and oil, and ac- CNO using two-step co-solvent method in a homogeneous celerates the reaction giving a high yield（＞95％）of FAME. system. The factors affecting BDF conversion efficiency, Furthermore, the co-solvent also accelerates phase separa- namely, alcohol types, catalysts, and molar ratios of metha- tion between FAME and the by-product glycerol upon nol to oil were investigated. FAME content and moisture completion of the reaction6, 7）. The transesterification reac- content attained in BDF was 99.3％ and 230 ppm, respec- tion has been carried out using various catalysts, such as tively. The physicochemical properties of the BDF were the alkaline catalysts sodium hydroxide（NaOH）, potassium compared with those of petro-diesel and evaluated on the 8, 9） hydroxide（KOH）, and sodium methoxide（CH3ONa） . basis of ASTM D6751-02 standard. The exhaust gases from Solid catalysts have also been examined for transesterifica- a diesel engine with electric power generator were exam- tion, but could not be applied to large scale BDF produc- ined using various blends of CNO BDF with petro-diesel in tion owing to the lower yield of FAMEs9）. the range from B0 to B100（biodiesel content 100％）. In an attempt to seek out a new feedstock for BDF production having reasonable cost and abundant availability, CNO was identified as a potential candidate. Candle tree （Aleurites moluccana）is a species of the Euphorbiaceae 2 EXPERIMENTAL PROCEDURES family, and found in many countries, such as China, India, 2.1 Materials Brazil, Malaysia, Vietnam, and Australia10）. In Vietnam, the Candlenuts were kindly gifted by the Institute of Chem- candle trees are cultivated and grow naturally in several istry, Vietnamese Academy of Science and Technology. provinces of the north-east regions and the highlands. Can- Kernels obtained after crushing candlenut seeds were ma- dlenut, a source of vegetable oil, is used for pharmaceuti- chine-pressed to extract CNO and/or extracted with n-hex- cal, cosmetic, industrial, and dietary applications11）. ane after homogenization. The photographs of candlenut Currently, in Asian countries, there have been a few seeds, their kernels and the CNO are shown in Fig. 1. The studies on use of CNO for producing BDF. The candlenut CNO content in kernel was around 230 g/kg. KOH（95.5％）, seeds contain approximately 30–40％ oil which can be ob- methanol（99％）, acetone（99.6％）, acetonitrile（99.7％）,

tained by compressing the kernels. The CNO contains large and CH3ONa（98％）were the analytical grade, and pur- quantities（around 70％）of unsaturated fatty acid moieties chased from Wako Pure Chemical Industries（Osaka,

as indicated by the high iodine number of 135（gI2/100g- Japan）. Chemical standards such as methyl oleate, methyl oil）. Thus, it exhibits a relatively high pour point, but gen- linoleate, monoolein, diolein, and triolein were obtained erally contains approximately 2–10％ free fatty acids from Sigma-Aldrich（Tokyo, Japan）, and heptadecanoic （FFAs）. acid was purchased from Wako Pure Chemical Industries. There have been a few reports on a two-step process using conventional heterogeneous method for BDF produc- 2.2 Two-step co-solvent procedure for biodiesel production from CNO. The BDF produced contained 7.8％ of tion FFAs, but required high energy consumption and longer In order to produce high quality BDF with more than time duration. Furthermore, water content less than 0.05％ 96％ FAME content, a two-step co-solvent method was could not be achieved10－12）. Comparison of gaseous emis- used. The procedures are shown in Fig. 2. The esterifica- sions from CNO BDF with petro-diesel, has been conducted tion of 6.9％ of FFAs in CNO using a co-solvent of acetoni-

Fig. 1 Candlenuts, kernels and candlenut oil. 618 J. Oleo Sci. 67, (5) 617-626 (2018) Production of Candlenut Oil Biodiesel Using Two-step Co-solvent Method and Gaseous Emission

Fig. 2 Scheme of esterification and transesterification processes for BDF production.

trile, and subsequent transesterification of the CNO and （methanol, ethanol, and 1-butanol）, of which molar ratio to produced FAMEs using a co-solvent of acetone were per- oil was 5/1 was added to the flask in order to evaluate the formed. effect of type of catalyst and alcohol used on the trans- Esterification using acetonitrile as a co-solvent was esterification reaction. This solution was stirred continu- carried out in order to reduce the content of FFAs13）. The ously for 1 h until maximum yield was obtained. After com- esterification process was carried out as follows: 100 g of pletion of the reaction, the mixture was transferred into a CNO was mixed with 30 g acetonitrile in a three-neck separatory funnel and allowed to stand for 30 min, follow- round bottom flask of 500 mL volume equipped with a con- ing which the lower glycerol layer was removed. The upper denser, a thermometer, and a nitrogen gas inlet. The reac- layer was distilled under reduced pressure to recover tion flask with a magnetic stirring bar in it, was placed in a acetone and methanol. The remaining mixture of FAMEs water bath maintained at 65℃. A mixture of sulfuric acid was neutralized with 5％ aqueous phosphoric acid, and pu- （1.0 g）and methanol（23 g）was added to the CNO solution. rified by washing with 50 mL of water repeatedly until the The esterification reaction was performed by gentle stir- washed water showed a pH of 7, and finally dried by distil- ring for 1 h. After esterification, the upper layer of CNO lation under reduced pressure at 85℃ for 40 min. The and the produced FAMEs（hereafter cited as crude CNO） refined BDF obtained was a clear light-yellow colored were purified by neutralization with aqueous NaOH solu- liquid. tion followed by washing with water, and drying under reduced pressure. 2.3 Analysis of physicochemical properties The second transesterification reaction was carried out The physicochemical properties of CNO and its BDF as follows: 85 g of the crude CNO obtained in the first es- were determined according to the ASTM D6751-02 terification was mixed with 17 g acetone（20 wt％ relative method. The acid value was determined by titration of a to oil）in a 250 mL three-neck round bottom flask and known concentration of KOH against 1 g of oil sample dis- placed in water bath maintained at 40℃. A solution of dif- solved in 10 mL of ethanol. The indicator used was phenol- ferent contents（0.5, 1.0, and 1.5 wt％ to oil）of catalyst phthalein. The acid value was calculated using the equation

（KOH, NaOH or CH3ONa）dissolved in various alcohols given below:

619 J. Oleo Sci. 67, (5) 617-626 (2018) L. N. Pham, B. V. Luu, H. D. Phuoc et al.

make-up helium gas were 40, 400, and 25 mL/min, respec- Acid value mgKOH/g N V 56.71 /W （）＝（ × × ） tively. An aliquot of 1 μL sample was injected using a split- where, N is equivalent concentration of KOH, V is volume less mode, and held for 1 min after injection. of KOH solution spent for titration（mL）, and W is weight of sample. 2.6 Determination of emission gas content FFAs content（％）was calculated using the following The experiments for monitoring gaseous emissions were equation: conducted using an electric generator SD3500EB（SAMDI Co., Taiwan）diesel engine composed of one cylinder and M/1000 100/W FFAs（％）＝V×N×（）×（） direct fuel injection system. The engine specifications are where, M is the average molecular weight of fatty acid, given in Table 1. The BDF blends with petro-diesel evalu- taken as 282. ated were 0％（ B0）, 5％（ B5）, 10％（ B10）, 20％（ B20）, 50％ Water content of oil and BDF was determined by Karl （B50）, and 100％（ B100）. All fuels were tested on engine Fisher Moisture titrator MKC-501（Kyoto electronic MFG drive with loads of 0％, 30％, 60％, and 100％. A class 1 Co., Ltd, Kyoto, Japan）. model of combustion and emission quality analyzer, with The concentrations of monoglyceride（MG）, diglyceride serial number N0356（KANE INTERNATIONAL LTD/OIML, （DG）, triglyceride（TG）, and FAMEs were determined by London, England）was used for quantification of emitted Gel Permeation Chromatography（GPC）. The GPC appara- gases. For monitoring of the pollutants, the probe of the tus consisted of a pump LC-10AD（Shimadzu Manufacture analyzer was connected to the outlet of gaseous stream Co. Ltd, Kyoto, Japan）and a refractive index detector and the values were measured after stabilization of engine RID-10A（Shimadzu）. The column used was an Asahipak driven at various engine loads corresponding to the per- GF 310 HQ（300 mm×7.5 mm, 5 μm）（ Shodex Co., Ltd, centage of electricity output to the maximum. The proce- Tokyo, Japan）. The temperature of column oven was 30℃, dure was run in triplicate for each loading. The measured acetone was used as the mobile phase at a flow rate of 0.5 gases were carbon monoxide（CO, non-dispersive infrared）, ml/min, and the sample injection volume was 20 μL. The nitrogen oxides（NOx, fuel cell）, and hydrocarbons（HC, FAME yields of the transesterification reaction were calcu- non-dispersive infrared）. lated by the following equation10, 14, 15）:

FAME yield（％）＝（ WFAME /MFAME）× 100（/ 3×WCNO /MCNO）

where, WFAME and WCNO represent the weights of FAMEs 3 RESULTS AND DISCUSSION

and CNO used respectively, while MFAME and MCNO are the 3.1 Physicochemical properties of candlenut oil molecular weights of FAMEs and CNO, respectively. The physicochemical properties of CNO are presented in Table 2. The oil content in nuts was 20–30 wt％. The iodine

2.4 Analysis of Fourier-transform infrared（FTIR）spectrum number was 138 gI2/100g-oil and was indicated by high The FTIR spectra were recorded in the range of 4000– value of kinematic viscosity of 24.9 mm2/s. The saponifica- 400 cm－1 using a RXI FTIR spectrometer（Perkin Elmer, tion value of CNO was 3.29 mgKOH/g. The high content of USA）equipped with KBr plates. The spectra were collected FFAs in the oils produces soaps（fatty acid salts）thereby in 40 （s 32 scans and 4 cm－1 resolution）. significantly affecting the transesterification reaction and ultimately the quality of BDF obtained. It is necessary to 2.5 Analysis of fatty acid components in CNO reduce the content of FFAs in the oil to less than 5 After transesterification of the CNO, the fatty acid moi- mgKOH/g of acid before transesterification. A two-step co- eties of glycerides in the form of methyl esters was determined using a gas chromatography-flame ionization Table 1 Specific ations of the tested SD3600EB detector（GC-FID）HP-6890 series（Agilent, CA, USA）according to the BS EN 140103:2003 method using an inter- engine. nal standard of heptadecanoic acid methyl ester. The ana- Parameters Values lytical column was a SPTM-2380 fused silica capillary Power permanent 3.7 kW/3000 rpm column（Spelco, USA, 30 m×0.25 mm, 0.2 μm）. The Power within 1 hour 4 kW/3000 rpm column temperature protocol was as follows: hold at 70℃ for 1 min, then increase to 120℃ at a rate of 20℃/min, Cylinder number 1 then increase to 240℃ at a rate of 4℃/min, and finally hold fuel combustion type Direct injection at 240℃ for 2 min. The temperatures of injector and detec- Cooling system air radiator tor were maintained at 250℃ each. The column flow rate Cylinder size 78×62 mm of helium gas was 1.0 mL/min. The flow rates for FID detector were as follows: flow rates of hydrogen, air, and the Displacement 0.296 Lit

620 J. Oleo Sci. 67, (5) 617-626 (2018) Production of Candlenut Oil Biodiesel Using Two-step Co-solvent Method and Gaseous Emission

Table 2 Characteristics of candlenut oil. Characteristics (Unit) Value Content (wt%) respective to nuts 20–30 Appearance Light yellow liquid Density, 20℃ (kg/m3) 914 Kinematic viscosity (mm2/s) 24.89

Iodine number (gI2/100g-oil) 138 FFA content (wt%) 6.9 Saponification (mgKOH/g) 3.29 Sediment amount (wt%) 0.02 Water content (wt%) 0.02 solvent method was examined for producing high quality BDF from CNO.

3.2 Esteri cation The first step of esterification was conducted according to the procedure reported by Luu et al.13）. Acetonitrile, a polar aprotic solvent promoting hydrolysis, was used as a co-solvent. The esterification parameters were as follows: sulfuric acid to oil ratio of 1 wt％, methanol to oil ratio of 23:100（w/w, in grams）, reaction temperature of 65℃, and reaction time of 1 h. After esterification, the phase separa- tion between the crude CNO and the acidic solvents was completed in 30 min, which took overnight when using Fig. 3 Effect of molar ratio of methanol to oil on biodiesel conventional heterogeneous method12）. The FFA content in conversion.（ acetone content 20 wt％, KOH the crude CNO was effectively reduced to 0.8％ following content 1％, reaction temperature 40℃, and which the oil could be subjected to transesterification reac- reaction time 45 min）. tion. conducted using ratio of 5/1. 3.3 Transesteri cation The effects of amounts of three catalysts namely, NaOH,

The transesterification reaction was conducted using a KOH, and CH3ONa on FAME yields were examined. The co-solvent of acetone. The parameters affecting the FAME experimental conditions were as follows: molar ratio of 5/1 yield such as catalyst types and types of alcohols used for methanol to oil, acetone to oil ratio of 20 wt％, reaction were evaluated. The optimal operational conditions for temperature of 40℃, and reaction time of 45 min. The CNO BDF production were compared with those applied to results of FAME yields are presented in Fig. 4. The FAME BDF production from Jatropha curcas oil containing 17％ yields of 99.3％ were attained when the KOH and NaOH of FFAs13）. content was 1 wt％. However, FAME yield reached 96.2％,

One of the most important variables affecting the FAME and 98％ with 0.3 wt％ and 0.5 wt％ CH3ONa respectively. yield is the molar ratio of methanol to oil. The FAME yield These results may be explained as follows: when NaOH was examined at different methanol to oil ratios of 3/1, 4/1, （or KOH）is dissolved in methanol, active methoxyl anions 5/1, 6/1, and 7/1. The reaction conditions were as follows: are formed according to the following equilibrium reaction: 20 wt％ acetone, 1％ KOH, reaction temperature of 40℃, Na or K OH CH OH CH ONa or K H O and reaction time of 45 min. The results are presented in （）＋ 3 ⇌ 3 （）＋ 2 Fig. 3. The stoichiometric molar ratio of methanol to oil is The transesterification reaction is preceded by formation 3/1. However, conversion efficiencies with molar ratios of of the methoxyl anions. The water molecules produced

3/1 and 4/1 were 59％ and 90％, respectively while a molar react with CH3ONa, thereby disturbing the forward reac- ratio of 5/1 gave 99％ efficiency. However, when using con- tion. On the other hand, methoxyl anions produced from ventional heterogeneous method for vegetable oils and CH3ONa catalyst can directly participate in the transesteri- animal fats, a ratio greater than 6/1 was required to achieve fication reaction in the absence of water. greater than 90％ yield16, 17）. All further experiments were FAME yield of more than 99％ could be achieved using

621 J. Oleo Sci. 67, (5) 617-626 (2018) L. N. Pham, B. V. Luu, H. D. Phuoc et al.

Fig. 4 Effect of catalysts and their amounts on FAME Fig. 5 Effect of alcohol types on FAME conversion.（ molar conversion.（ molar ratio of alcohol to oil was 5/1, ratio of alcohol to oil was 5/1, acetone amount to acetone amount to oil was 20 wt％, temperature of oil 20 was wt％, reaction temperature of 40℃,

40℃, and reaction time of 45 min）. reaction time of 45 min, and CH3ONa catalyst amount of 0.5 wt％）. both, NaOH and KOH as catalysts. KOH catalyst was used for the CNO BDF production because of its greater solubil- 3.4 Characterization of candlenut oil biodiesel ity in methanol. It has been reported that KOH catalyst of The physicochemical properties of the CNO BDF are 1.0–1.25％ was suitable for transesterification of CNO presented in Table 3. The water content was as low as 230 using conventional heterogeneous method10, 18）. ppm. The dewatering process discussed in the procedure The FAME yields in presence of various types of alco- of transesterification successfully reduced water content hols, such as, methanol, ethanol, and 1-butanol were exam- to 0.02％（ 200 ppm）. Water if present, can cause serious ined. The experimental conditions were as follows: acetone problems for the material of the engine, and cause deterio- to oil ratio of 20 wt％, molar ratio of alcohol to oil was 5/1, ration of BDF during storage. The FAME content was as reaction temperature of 40℃, and amount of CH3ONa cata- high as 99.3％. The content of FFAs was 0.21 mgKOH/g. lyst was 0.5 wt％. The effects of alcohol type on FAME The kinematic viscosity（at 40℃）was 4.24 mm2/s and com- yield are presented in Fig. 5. After 30 min, methanol gave parable with that of petro-diesel. The viscosity of fuel 96％ FAME yield, while ethanol and 1-butanol gave 94％, affects the fuel delivery rate, the atomization of fuel during and 90％ yields of FAMEs respectively. These results indi- injection, and the lubrication of the engine18）. The CNO cated that the reaction rate was dependent on bulkiness of BDF had a cloud point of 5.0℃, and a pour point of 6.3℃, the alkoxyl anion（RO－）produced from alcohol by catalytic similar to those of petro-diesel. The cloud and pour points reaction of CH3ONa. The small methoxyl group of methanol of BDF vary significantly with fatty acid compositions of can easily attack carboxyl groups of glycerides, thus allow- feedstock19）. ing the reaction to proceed rapidly. Hence, methanol is the most suitable reagent among the tested alcohols for BDF 3.5 FTIR spectrum of candlenut oil biodiesel production. The FTIR spectrum of CNO BDF is shown in Fig. 6. The FAMEs in BDF have unique absorptions, distinct from

Table 3 Physicochemical properties of candlenut oil biodiesel and petro diesel. Properties (Unit) Candlenut biodiesel Petro-diesel Standards* FAME content (mass%) 99.3 － 96.5 Density, 20℃ (kg/m3) 887 820-870 － Kinematic Viscosity, 40℃ (mm2/s) 4.24 2.58 1.9-6.0 Water content (mg/kg) 230 200 <500 Cloud point (℃) 5.0 －－ Pour point (℃) 6.3 6.0 － Ash content (%) 0.008 <0.01 <0.02 Acid value (mgKOH/g) 0.21 － 0.50 max *) ASTM D6751-02 standard

622 J. Oleo Sci. 67, (5) 617-626 (2018) Production of Candlenut Oil Biodiesel Using Two-step Co-solvent Method and Gaseous Emission

Fig. 6 FTIR spectrum of CNO biodiesel.

*1 Table 4 Main components of fatty acid in oils（wt％）. Candlenuts Fatty acids Rubber seed*3 Vernicia montana*4 present work Ref*2 palmitic acid (C16:0) 6.3 8.0 7.2 2.2 stearic acid (C18:0) 3.2 2.1 4.8 1.9 oleic acid (C18:1) 21.8 22.6 24.5 6.5 10-octadecenoic acid (C18:1) 0.6 1.1 －－ linoleic acid (C18:2) 41.1 38.1 42.3 8.5 a-linolenic acid (C18:3) 26.8 28.1 21.0 － g-linolenic acid 0.3 －－－ α-eleostearic acid (C18:3) －－－ 80.3 others －－ 1.0 0.6 *1 determined after esterification and transesterification processes *2 cited in the reference20) *3 cited in the reference21) *4 cited in the reference22) components in petro-diesel, at 1735 cm－1 owing to the C＝ sponding to –OH stretching vibration indicates that the －1 －1 O stretching vibrations and at 1168 cm , 1199 cm , and methanol used as reagent was converted to –OCH3 and 1247 cm－1 owing to the C–O bending. The weak signal at removed by the purification process. In summary, the ob- 1647 cm－1 may be because of C＝C stretching vibration. tained CNO BDF was characterized using FTIR spectrum. The strong peaks from 2854 cm－1 to 2924 cm－1 show the presence of –CH2 asymmetric stretching. The absorbance 3.6 Fatty acid components in candlenut oil bands of 3004 cm－1 and 1460 cm－1 indicate the ＝C–H The fatty acid moieties of CNO were converted into their stretching and the –CH2 scissor stretching, respectively. methyl esters by the previously described transesterifica- The most distinguished absorption displayed by the trans- tion process. The results are shown in Table 4. The compo- esterification product is the signal at 1436 cm－1 attributed nents of biodiesels produced from CNO cultivated in to deformation vibrations of the methyl ester group, that is Cuba20）, rubber seed oil21）, and Vernicia montana oil22）are absent in CNO. The lack of the peak at 3500 cm－1 corre- also presented for comparison. The main components in

623 J. Oleo Sci. 67, (5) 617-626 (2018) L. N. Pham, B. V. Luu, H. D. Phuoc et al.

CNO cultivated in Vietnam were palmitic acid（C16:0）, sel at various engine loads are shown in Fig. 7（a）. Upon in- stearic acid（C18:0）, oleic acid（C18:1）, linoleic acid creasing the engine load, the CO emissions decreased with （C18:2）, and linolenic acid（C18:3）which were very similar increasing percentages of BDF blend. A 60％ reduction in to those obtained from CNO in Cuba and rubber seed oil. CO emission was observed when B100 was used at 100％ The total unsaturated fatty acid content was as high as load when compared to that when B0 was used. By increas- 90％. Parameters such as iodine index, kinematic viscosity, ing the engine load, the fuel undergoes complete combus- and pour and cloud points affect the operation of diesel tion in the engine cylinder because of increased availability engine. The BDF of Vernicia montana oil containing 80％ of oxygen or air supply which reduces CO emission and in- of α-eleostearic acid methyl ester consisting of three con- creases engine temperature. The inverse proportion of CO jugated double bonds in the molecule presented an iodine emission to the percentage of BDF blends can be attributed 23） number of 158 gI2/100g-oil, which is an indicator of the to fuel oxygen mass as suggested by Raslavičius et al. . degree of unsaturation in the oil, and kinematic viscosity of There have been many reports on reduction of CO emis- 7.7 mm2/s（40℃）. sion upon BDF（B100）combustion in comparison with petro-diesel（B0）: an average 50％ reduction from various 3.7 Gaseous emissions from diesel engine combustion of BDF15）, 32.2％ reduction from sunflower oil BDF24）, and candlenut oil biodiesel 55％ reduction from rapeseed oil BDF23）. Using blends of The emission gases from one cycle diesel engine with waste oil BDF25）, it was verified that B25 and B75 reduced electric power generator were examined. Combustion of the CO emissions by 2 to 13％, respectively. the CNO BDF（B100）and its blends（B50, B20, B10, and The results of NOx emissions are shown in Fig. 7（b）. An B5）with petro-diesel（B0）were tested in the diesel engine. increase in the engine load increases NOx concentration The diesel engine loads were varied at 0％, 30％, 60％, and regardless of the BDF blends used. In comparison with 100％. The results are shown in Fig. 7. petro-diesel（B0）, NOx emissions increased with an in- The CO emissions by various BDF blends with petro-die- crease in BDF blends from B0 to B100. A 70％ increase in

Fig. 7 Effect of biodiesel blends and engine load on gaseous emissions. 624 J. Oleo Sci. 67, (5) 617-626 (2018) Production of Candlenut Oil Biodiesel Using Two-step Co-solvent Method and Gaseous Emission

NOx emission using B100 was observed in comparison to and economical manner, with less energy consumption B0 when used at 100％ load. These results were supported compared to the conventional heterogeneous method. The by studies on BDF combustion: approximately 11.6％ in- exhaust gas from an electric power generator was evaluat- crease of NOx emission from BDF（B100）was observed ed. The amounts of CO as well as HC emission driven by when compared to those from petro-diesel（B0）26）, and the CNO BDF（B100）at 100％ engine load were clearly lower NOx emissions increased proportionally to fuel oxygen by 60％ each when compared to those with petro-diesel mass23）. It has been shown that the increase in NOx emis- （B0）, while the amount of NOx emission was 70％ higher. sions is a signal of higher heat release and may be explained by the cetane number as well as relate to the oxygen molecules present in the compound27）. A 19.4％ reduction in NOx emission was observed in BDF（B100）from ACKNOWLEDGMENT waste flying oil when compared to petro-diesel（B0）19）. The This study was supported by Vietnam Counterpart combustion efficiency of BDF containing oxygen in its mol- finance of the Science and Technology Research Partner- ecule is higher in comparison to that of petro-diesel. As a ship for Sustainable Development Project（SATREPS result, the NOx emission, wherein nitrogen is obtained Project）:“ Multi-beneficial Measures for Mitigation of from ambient air, increases accompanied with an increase Climate Change in Vietnam and Indochina Countries by in combustion temperature of the engine. Development of Biomass Energy, JST-JICA”. The results of HC emissions are shown in Fig. 7（c）. The trends of HC emissions were quite similar to CO emissions: HC emission decreased with increase in engine load and percentages of BDF blends. 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