View Article Online / Journal Homepage / Table of Contents for this issue Green Chemistry Dynamic Article Links Cite this: Green Chem., 2011, 13, 1124 www.rsc.org/greenchem COMMUNICATION Published on 22 March 2011 Downloaded by Anadolu University on 12/05/2014 10:16:49 New technology for the production of biodiesel fuel† Yasuaki Maeda,a Le Tu Thanh,a Kiyoshi Imamura,a Katsutoshi Izutani,a Kenji Okitsu,b Luu Van Boi,c Pham Ngoc Lan,c Nguyen Cong Tuan,c Young Eok Yood and Norimichi Takenakab Received 14th January 2011, Accepted 25th February 2011 DOI: 10.1039/c1gc15049a A new, homogeneous method for producing biodiesel fuel (BDF), achieving a minimum emission of waste and a low consumption of energy, was developed by adding organic solvents such as acetone to a reaction mixture of oil and methanol with an alkaline catalyst By adding acetone and a smaller amount of catalyst at room temperature, fatty acid methyl ester (FAME) was formed within with a quality satisfying the international BDF standards, even in the coexistent of water in the raw material The difference in the kinetic data when using isopropyl alcohol (IPA) (all compounds are in a single phase) and acetone (all compounds except glycerin are in a single phase), shows that the retardation of FAME formation in the presence of glycerin product is not due to the reverse reaction but to the removal of methanol and KOH catalyst from the reaction phase by the precipitated glycerin produced during the final stages of the reaction The former Japanese Prime Minister Yukio Hatoyama declared at the United Nations Summit on Climate Change in 2009 that Japan will aim to reduce CO2 emissions by 25% by 2020 compared with the 1990 level The USA President Barack Obama’s green dream team also declared that the USA will be committed to battling climate change as one of the leaders of reducing global warming As alternatives to wind power generation and solar batteries, biomass energy resources such as methane, ethanol and BDF have attracted much attention for the mitigation of global warming due to the carbon neutrality of biomass BDF production from vegetable oil is the most popular because the formation process is faster and simpler than methane or ethanol production Therefore, more than 10 million tons of BDF were produced in EU countries mainly from rape seed oil a Organization for Industry, University and Government Cooperation, Osaka Prefecture University, 1–2 Gakuen-cho, Naka-ku, Sakai, 599-8531, (Japan) E-mail: y-maeda@chem.osakafu-u.ac.jp; Fax: +81-72-254-9863; Tel: +81-72-254-9863 b Graduate school of Engineering, Osaka Prefecture University, (Japan) E-mail: okitsu@mtr.osakafu-u.ac.jp c Viet Nam National University, Hanoi, (Vietnam) d Daegu University, (Korea) † Electronic supplementary information (ESI) available See DOI: 10.1039/c1gc15049a 1124 | Green Chem., 2011, 13, 1124–1128 and in the USA from soy bean oil in 2010, even though they are edible oils.1 However, some questions remain: (1) What is the best raw material available that does not increase food prices or deforestation? (2) What is the best production method for a green process by which fatty acid methyl ester (FAME) can be obtained with a minimal emission of waste and low energy consumption? Many chemists have attempted to meet these requirements.2–7 One solution proposed to reduce the formation of soap with an alkaline catalyst was the application of an enzyme catalyst, but the reaction rate was too slow.8–10 Jordan and Gutsche11 have reported the simultaneous separation of glycerin with a membrane Aßmann et al.12 reported a two step reaction to increase the yield of FAME with a smaller amount of methanol The BDF production from waste cooking oil by a conventional mechanical stirring method requires the pretreatment of raw material oil and the distillation of the final product to pass the EU or USA standards of BDF In 1960 Por´e, and in 1984 Freedman et al., reported the transesterification of vegetable oil with methanol and described the reaction scheme as follows: TG + CH3 OH FAME + DG (1) DG + CH3 OH FAME + MG (2) MG + CH3 OH FAME + GL (3) where TG: triglyceride; DG: diglyceride; MG: monoglyceride; and GL: glycerin They also reported that the reaction rate became slower after the formation of GL due to reverse reactions of (1) to (3) and added excess amounts of methanol to oil (6 : molar ratio) to accelerate the forward reactions All subsequent scientific papers followed the Freedman’s paper.13–15 However, no one has confirmed the involvement of the reverse reactions In this paper, we have examined the reverse reactions and found the decrease in the BDF production rate was not due to the reverse reactions but to the elimination of the important methanol reactant by its dissolution in GL The reaction was accelerated without heating, using small amounts of alkaline catalyst, by adding a suitable co-solvent Furthermore, the separation of GL from FAME was accelerated in the presence of acetone Here, we report the development of a new, green production method for BDF This journal is © The Royal Society of Chemistry 2011 View Article Online Table Dissolution of reactants and products in organic solvents (20 ◦ C) Published on 22 March 2011 Downloaded by Anadolu University on 12/05/2014 10:16:49 Solvents Compounds H2 O CH3 OH Acetone THF IPA ANa DE FAME TG FAME GL CH3 OH Oleic acidb , c Stearic acidb , c Soap ¥ ¥ ¥ ¥ ᭺ ᭺ ᭺ ᭺ ᭺ ᭺ ᭺ ᭺ ᭺ ¥ ᭺ ᭺ ᭺ ᭺ ᭺ ᭺ ᭺ ᭺ ᭺ ¥ ᭺ ᭺ ¥ ¥ ¥ ¥ ᭺ ᭺ ᭺ ¥ ᭺ ᭺ ᭺ ᭺ ¥ ᭺ ¥ ᭺ ¥ ¥ ¥ ¥ ¥ ¥ ¥ ᭺ ᭺ ᭺ ᭺ soluble, ᭺: was ◦ : slightly soluble, ¥: not soluble.a AN: acetonitrile b FAME (methyl oleate) c Melting points of oleic acid and stearic acid are 16.3 C and 69.9 ◦ C, respectively How can we accelerate the formation of FAME in the reaction between the immiscible oil and methanol? One approach is to accelerate the reaction by heating and another is to accelerate it by increasing the contact interface by forming small reactant droplets through vigorous stirring by ultrasonic irradiation.16–19 Even so, the reaction can still only take place at the interface between the immiscible reactants present in the heterogeneous phases If the FAME formation takes place in a homogeneous phase, the reaction can be accelerated by a molecular-molecular reaction Boocock et al 20 achieved acceleration of the FAME formation by adding tetrahydrofuran (THF) or diethyl ether (DE) but reported only that the reaction could be accelerated Therefore, we have studied the selection of the best solvent for both formation and separation of FAME and elucidated the role of solvents in FAME formation As shown in Table 1, methanol, TG and FAME were easily dissolved in acetone or in THF, but GL was not In contrast, IPA dissolves all compounds related to the transesterification of oil namely TG, FAME, GL, methanol and KOH catalyst As a result, the transesterification of oil with methanol to produce FAME can be performed partially in the homogeneous phase with acetone and THF until GL is formed and completely in the homogeneous phase with IPA As shown in Fig 1, the formation rate of FAME in acetone is much faster than that without solvent and is the fastest among the solvents with the addition of a 4.5 : molar ratio of methanol to oil Moreover, the retardation of FAME formation could be observed clearly in the heterogeneous system without solvent On the other hand, in the case of IPA, the reaction occurred in the homogeneous system As shown in Fig 2a and 2b, the formation rate with IPA was very fast even at a : molar ratio of methanol addition Furthermore, the formation of FAME and consumption of methanol could reach stoichiometric completion even with addition of : 1, : and : molar ratios of methanol to oil in the homogeneous phase with IPA We concluded that there is no reverse reaction in the homogeneous system The formation of the fatty acid isopropyl ester was only about 1% of the formation of methyl ester, due to the steric hindrance of the isopropyl group Therefore, the IPA reaction is neglected in further discussion Why does the FAME formation reaction rate slow down in the final stages of the reaction? Is it due to the reverse reaction of the products to the original reactants, as proposed by Freedman et al.? The reaction of methyl oleate, with GL, This journal is © The Royal Society of Chemistry 2011 Fig Effect of solvent on the FAME yield (᭛) acetone, ( ) IPA, ( ) THF, (¥) DE, (᭹) AN, (᭺) without solvent Conditions: molar ratio of methanol to canola oil, 4.5 : 1; solvent to oil, 25 wt%; KOH to oil, 0.5 wt%; temperature, 20 ◦ C monoolein, and diolein from 20 ◦ C to 60 ◦ C with and without KOH catalyst has been studied to elucidate the reason for the reaction retardation after GL formation However, as shown in Table 2, no reverse reaction could be observed, even after one week From this result, the retardation of FAME formation is not due to the reverse reactions of equilibrium reactions (1)–(3) and the retardation must occur through other phenomena From the results shown in Table and Fig and 2, we have concluded that the retardation of FAME formation after the formation of GL can be explained as follows: in the case without solvent, or with acetone or THF, GL cannot be dissolved in the oil or FAME, but methanol and KOH catalyst dissolve well in GL Therefore, FAME formation is retarded after the formation of GL due to the dissolution of the important reactant methanol and the catalyst into the GL phase, which easily precipitates and is excluded from the reactant solution On the other hand, FAME formation is not retarded and does not require excess methanol in the presence of IPA, which forms a homogeneous solution that includes GL, as shown in the supplementary data photograph S1a.† As described above, FAME could be effectively produced by the co-solvent method with acetone or IPA However, as shown in the supplementary data photographs S1a and b,† the separation of FAME from GL is completely different when using Green Chem., 2011, 13, 1124–1128 | 1125 View Article Online Table Confirmation of the reverse reactions Reactant Published on 22 March 2011 Downloaded by Anadolu University on 12/05/2014 10:16:49 GL GL MG MG DG DG FAME FAME FAME FAME FAME FAME Molar ratio KOH wt% Result FAME/GL = FAME/GL = FAME/MG = FAME/MG = FAME/DG = FAME/DG = 0.5 0.0 0.5 0.0 0.5 0.0 No formation of MG, DG, TG No formation of MG, DG, TG No formation of DG, TG No formation of DG, TG No formation of TG No formation of TG GL: glycerin, FAME: oleic acid methyl ester, MG: oleic acid mono-glyceride, DG: oleic acid di-glyceride All results were obtained in the reaction with both the co-solvent and conventional mechanical stirring method at 20–60 ◦ C for 168 h (7 days) gravity and viscosity between the two phases The specific gravities and viscosities of FAME with the solvents is shown in the supplementary data Table S1.† The specific gravities of the GL phase were GL + methanol : (0.9870) < GL + methanol : (1.111) < neat GL (1.2632) Therefore, in the presence of acetone, the difference in specific gravity between FAME in acetone (0.8395) and GL with one mole of excess methanol (1.111) is 0.2715 Due to the large difference in specific gravity and small viscosities of the two components, GL was rapidly separated from the FAME solution and precipitated within 30 On the other hand, with the conventional mechanical stirring methods, scientists have used a methanol/oil ratio of Therefore, the separation of FAME from GL took a long time because the difference in specific gravity between FAME and GL was small, only 0.1077 (This calculation is based on the assumption that an excess moles of methanol are dissolved in GL, for which the specific gravity is 0.9870, and the specific gravity of neat FAME is 0.8793) The effect of water on the formation of FAME is very important when waste cooking oil was used as the raw material As shown in Fig 3, the formation of FAME even in the presence of wt% of water was not retarded in the co-solvent method In contrast, the yield of FAME at 60 became ca 15% in the presence of wt% of water in the conventional mechanical stirring method Fig a) Effect of methanol amount on the FAME yield and b) change in methanol concentration (C : concentration of methanol at time 0, C t : concentration of methanol at time t) Conditions: molar ratio of methanol to canola oil (᭛) : 1, (᭺) : 1, ( ) : 1, ( ) : 1; KOH to oil, 0.5 wt%; co-solvent IPA to oil, 25 wt%; temperature, 20 ◦ C acetone or IPA With acetone, which does not dissolve GL, the separation of FAME from GL was very fast because of the lower viscosity of the FAME-acetone solution and the large difference between the low-density FAME-acetone solution and GL In contrast, with IPA, the solution was homogeneous even after the formation of GL and the separation was not observed as seen in the supplementary data photograph S1a.† However, after the removal of IPA from the solution, GL and FAME were completely separated Why can the separation of FAME from GL be accelerated with acetone? The gravimetric separation can be accelerated mainly through two factors which are the differences in specific 1126 | Green Chem., 2011, 13, 1124–1128 Fig The effect of water on the formation rate of FAME (᭛) wt% water, co-solvent; ( ) wt% water, co-solvent; ( ) wt% water, mechanical stirring; (᭺) wt% water, mechanical stirring Conditions: molar ratio of methanol to waste cooking oil, 4.5 : 1; acetone to oil, 25 wt%; KOH to oil, 0.5 wt%; temperature, 20 ◦ C This journal is © The Royal Society of Chemistry 2011 View Article Online Table Properties of biodiesel produced from cat fish oil or Jatropha Curcas oil at pilot plant scale with a capacity of 300 L/batch under the condition: molar ratio of methanol to oil, 4.5 : 1; acetone to oil, 25 wt%; KOH catalyst to oil, 0.5 wt%; temperature, 25 ◦ C Published on 22 March 2011 Downloaded by Anadolu University on 12/05/2014 10:16:49 Result (%) JIS K2390 Test parameter Unit Cat fish Jatropha Min Max Test method Total ester MG DG TG Free GL Total GL Acid value Iodine value Methanol Water content Mass (%) Mass (%) Mass (%) Mass (%) Mass (%) Mass (%) mg KOH g-1 g I2 /100 g Mass (%) mg kg-1 97.5 0.40 0.10