Journal of Oleo Science Copyright ©2018 by Japan Oil Chemists’ Society doi : 10.5650/jos.ess17220 J. Oleo Sci. 67, (5) 617-626 (2018) 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 pro- duction 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 produc- tion 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℃.