Energy Fuels 2010, 24, 3906–3916 Published on Web 06/15/2010
: DOI:10.1021/ef100484q
Experimental and Modeling Study of the Kinetics of Oxidation of Simple Biodiesel-Biobutanol Surrogates: Methyl Octanoate-Butanol Mixtures C. Togbe,† G. Dayma,†,‡ A. Mze-Ahmed,† and P. Dagaut*,† †
Centre National de la Recherche Scientifique, INSIS, ICARE 1C, Avenue de la Recherche Scientifique, 45071 Orl eans Cedex 2, France, and ‡University of Orl eans, Facult e des Sciences, 45067 Orl eans Cedex 2, France Received April 16, 2010. Revised Manuscript Received June 3, 2010
There is growing interest for using butanol-biodiesel fuel blends in diesel engines, but neither kinetic data nor kinetic models were available for simulating their combustion. Therefore, the kinetics of oxidation of a biodiesel-biobutanol surrogate fuel (methyl octanoate-1-butanol) was studied experimentally in a jet-stirred reactor (JSR) at 10 atm, at a constant mean residence time of 0.7 s, over the temperature range 560-1190 K, and for several equivalence ratios ranging from 0.5 to 2. Concentration profiles of reactants, stable intermediates, and final products were determined as a function of temperature, by low-pressure sonic probe sampling followed by online Fourier transform infrared spectrometry (FTIR), and off-line gas chromatography (GC) analyses with thermal conductivity (TCD), flame ionization (FID), and mass spectrometry (MS) detection. The oxidation of this fuel in the aforementioned conditions was modeled using a detailed chemical kinetic reaction mechanism consisting of 4545 reactions and 1098 species. The proposed kinetic reaction mechanism generally yielded a good representation of the kinetics of oxidation of this biodiesel-biobutanol surrogate under the present conditions. The kinetic modeling was used to delineate the reactions enhancing the low-temperature oxidation of 1-butanol, important for diesel and HCCI engine applications. The present results also indicated that the methyl octanoate-1-butanol mixtures are less prone to emitting acetaldehyde than the corresponding methyl octanoate-ethanol mixtures oxidized in a JSR.
biodiesel may help preserving our environment.4,6 Current biodiesel fuels are mixtures of ∼C12-C22 highly saturated carbon chain esters. Their complex composition implies the use of surrogate model-fuels for simulating their combustion kinetics. Early kinetic studies have shown a strong similitude between the oxidation of n-hexadecane and that of rapeseed oil methyl esters (RME),7,8 permitting the use of n-hexadecane as a chemical model-fuel for RME’s oxidation modeling. Simple methyl esters were also considered as surrogates.9 Latter, longchain methyl esters were also proposed as biodiesel model fuels.8,10,11 Methyl octanoate, for which a combustion scheme of reasonable size can be proposed, seems to be a valuable surrogate too.12
1. Introduction It is expected that, due to their high efficiency,1 diesel engines will continue to be used over the next decades. However, they contribute significantly to carbon dioxide emissions whereas concerns about global warming and air pollution are growing. Additionally, the gap between the growth rate of oil production and demand is increasing, implying a need for exploration for sustainable and environment-friendly diesel fuels. Biofuels derived from renewable resources may be considered sustainable if sufficient quantities of plants can be grown while mitigating the associated carbon footprint. Biofuels such as fatty acid methyl esters (FAME) can be mixed in variable quantities with fossil diesel fuel.2-4 The so-called biodiesel is a mixture of FAME obtained from mostly vegetable renewable lipid feedstock.5 They are catalytically obtained together with glycerol by transesterification of triglycerides (oils) with methanol. Reduction of engines emissions of fossil carbon oxides and polyaromatic hydrocarbons (PAH) have been reported, indicating
(6) Ilkilic, C. Emission Characteristics of a Diesel Engine Fueled by 25% Sunflower Oil Methyl Ester and 75% Diesel Fuel Blend. Energy Sources, Part A: Recovery Util. Environ. Eff. 2009, 31 (6), 480–491. (7) Dagaut, P.; Gail, S.; Sahasrabudhe, M. Rapeseed oil methyl ester oxidation over extended ranges of pressure, temperature, and equivalence ratio: Experimental and modeling kinetic study. Proc. Combust. Inst. 2007, 31 (2), 2955–2961. (8) Herbinet, O.; Pitz, W. J.; Westbrook, C. K. Detailed chemical kinetic oxidation mechanism for a biodiesel surrogate. Combust. Flame 2008, 154 (3), 507–528. (9) Gail, S.; Thomson, M. J.; Sarathy, S. M.; Syed, S. A.; Dagaut, P.; Dievart, P.; Marchese, A. J.; Dryer, F. L. A wide-ranging kinetic modeling study of methyl butanoate combustion. Proc. Combust. Inst. 2007, 31 (1), 305–311. (10) Dayma, G.; Gail, S.; Dagaut, P. Experimental and kinetic modeling study of the oxidation of methyl hexanoate. Energy Fuels 2008, 22 (3), 1469–1479. (11) Zhang, Y.; Yang, Y.; Boehman, A. L. Premixed ignition behavior of C9 fatty acid esters: A motored engine study. Combust. Flame 2009, 156 (6), 1202–1213. (12) Togbe, C.; May-Carle, J. B.; Dayma, G.; Dagaut, P. Chemical Kinetic Study of the Oxidation of a Biodiesel-Bioethanol Surrogate Fuel: Methyl Octanoate-Ethanol Mixtures. J. Phys. Chem. A 2010, 114 (11), 3896–3908.
*To whom correspondence should be addressed. Telephone: (þ33) 238 255466. Fax: (þ33) 238 696004. E-mail:
[email protected]. (1) Song, C.; Hsu, C. S.; Mochida, I. Chemistry of Diesel Fuels; Taylor & Francis: London, 2000. (2) Montagne, X. Introduction of Rapeseed Methyl Ester in Diesel Fuel--The French National Program. SAE Technical Paper 962065, 1996. (3) Graboski, M. S.; McCormick, R. L. Combustion of fat and vegetable oil derived fuels in diesel engines. Prog. Energy Combust. Sci. 1998, 24 (2), 125–164. (4) Ryan, T. W.; Mehta, D.; Callahan, T. J., HCCI: Fuel and engine interaction. In Which Fuels for Low CO2 Engines? Duret, P., Montagne, X., Eds. Technip: Paris, France, 2004; pp 59-67. (5) Ryan, L.; Convery, F.; Ferreira, S. Stimulating the use of biofuels in the European Union: Implications for climate change policy. Energy Policy 2006, 34 (17), 3184–3194. r 2010 American Chemical Society
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Energy Fuels 2010, 24, 3906–3916
: DOI:10.1021/ef100484q
Togbe et al.
Alcohols produced from biomass via various processes represent attractive renewable liquid fuels for ground transportation. At present, ethanol is increasingly used in spark ignition (SI) engines,13-15 whereas its use in diesel engines is difficult due to its very low cetane number and low solubility in fossil diesel fuel. Nevertheless, there is increasing interest for using reformulated diesel fuels containing ethanol16-33 with
Table 1. Oxidation of Methyl Octanoate-Butanol Mixtures in a JSR at 10 atm and 0.7 s: Experimental Conditions initial mole fractions methyl octanoateequivalence methyl 1-butanol (mol %) ratio, j octanoate 50-50 80-20
(13) Jeuland, N.; Montagne, X.; Gautrot, X., Potentiality of ethanol as a fuel for dedicated engine. In Which Fuels for Low CO2 Engines? Duret, P., Montagne, X., Eds. Technip: Paris, France, 2004; pp 7-19. (14) Dagaut, P.; Togbe, C. Experimental and modeling study of the kinetics of oxidation of ethanol-gasoline surrogate mixtures (E85 surrogate) in a jet-stirred reactor. Energy Fuels 2008, 22 (5), 3499–3505. (15) Lu, X. C.; Hou, Y. C.; Zu, L. L.; Huang, Z. Experimental study on the auto-ignition and combustion characteristics in the homogeneous charge compression ignition (HCCI) combustion operation with ethanol/n-heptane blend fuels by port injection. Fuel 2006, 85 (17-18), 2622– 2631. (16) Pang, X. B.; Shi, X. Y.; Mu, Y. J.; He, H.; Shuai, S. J.; Chen, H.; Li, R. L. Characteristics of carbonyl compounds emission from a dieselengine using biodiesel-ethanol-diesel as fuel. Atmos. Environ. 2006, 40 (36), 7057–7065. (17) Chen, H.; Shi-Jin, S.; Jian-Xin, W. Study on combustion characteristics and PM emission of diesel engines using ester-ethanol-diesel blended fuels. Proc. Combust. Inst. 2007, 31 (2), 2981–2989. (18) Guo, Y. S.; Zhong, J.; Xing, Y.; Li, D.; Lin, R. S. Volatility of blended fuel of biodiesel and ethanol. Energy Fuels 2007, 21 (2), 1188– 1192. (19) Jordanov, D. I.; Dimitrov, Y. K.; Petkov, P. S.; Ivanov, S. K. Study on the performance characteristics of mixtures of biodiesel, conventional diesel and ethanol. Oxid. Commun. 2007, 30 (4), 865–875. (20) Kwanchareon, P.; Luengnaruemitchai, A.; Jai-In, S. Solubility of a diesel-biodiesel-ethanol blend, its fuel properties, and its emission characteristics from diesel engine. Fuel 2007, 86 (7-8), 1053–1061. (21) Pang, X. B.; Mu, Y. J.; Yuan, J.; He, H. Carbonyls emission from ethanol-blended gasoline and biodiesel-ethanol-diesel used in engines. Atmos. Environ. 2008, 42 (6), 1349–1358. (22) Park, S. H.; Yoon, S. H.; Suh, H. K.; Lee, C. S. Effect of the Temperature Variation on Properties of Biodiesel and Biodiesel-Ethanol Blends Fuels. Oil Gas Sci. Technol. 2008, 63 (6), 737–745. (23) Cheenkachorn, K.; Fungtammasan, B. Biodiesel as an Additive for Diesohol. Int. J. Green Energy 2009, 6 (1), 57–72. (24) Guarieiro, L. L. N.; de Souza, A. F.; Torres, E. A.; de Andrade, J. B. Emission profile of 18 carbonyl compounds, CO, CO2, and NOx emitted by a diesel engine fuelled with diesel and ternary blends containing diesel, ethanol and biodiesel or vegetable oils. Atmos. Environ. 2009, 43 (17), 2754–2761. (25) Jha, S. K.; Fernando, S.; Columbus, E.; Willcutt, H. A Comparative Study of Exhaust Emissions Using Diesel-Biodiesel-Ethanol Blends in New and Used Engines. Trans. ASABE 2009, 52 (2), 375–381. (26) Shudo, T.; Nakajima, T.; Hiraga, K. Simultaneous reduction in cloud point, smoke, and NOx emissions by blending bioethanol into biodiesel fuels and exhaust gas recirculation. Int. J. Engine Res. 2009, 10 (1), 15–26. (27) Yoon, S. H.; Park, S. H.; Suh, H. K.; Lee, C. S. Effect of Biodiesel-Ethanol Blended Fuel Spray Characteristics on the Reduction of Exhaust Emissions in a Common-Rail Diesel Engine. Es2008: Proceedings of the 2nd International Conference on Energy Sustainability-2008, Vol. 1, 2009; pp 463-470. (28) Pidol, L.; Lecointe, B.; Jeuland, N. In Ethanol as a Diesel Base Fuel: Managing the Flash Point Issue-Consequences on Engine Behaviour, Powertrains, Fuels and Lubricants Meeting, Florence, Italy, June 2009; Session: Alternative and Advanced Fuels, SAE 2009-01-1807. (29) Pidol, L.; Lecointe, B.; Pesant, L.; Jeuland, N. Ethanol as a Diesel Base Fuel Potential in HCCI Mode, Powertrains, Fuels and Lubricants Meeting, Chicago, IL, October 2008; Session: Alternative Fuels, SAE 2008-01-2506. (30) Chotwichien, A.; Luengnaruemitchai, A.; Jai-In, S. Utilization of palm oil alkyl esters as an additive in ethanol-diesel and butanol-diesel blends. Fuel 2009, 88 (9), 1618–1624. (31) Pang, X.; Mu, Y.; Yuan, J.; He, H. Carbonyls emission from ethanol-blended gasoline and biodiesel-ethanol-diesel used in engines. Atmos. Environ. 2008, 42 (6), 1349–1358. (32) Shi, X.; Pang, X.; Mu, Y.; He, H.; Shuai, S.; Wang, J.; Chen, H.; Li, R. Emission reduction potential of using ethanol-biodiesel-diesel fuel blend on a heavy-duty diesel engine. Atmos. Environ. 2006, 40 (14), 2567– 2574. (33) Shi, X.; Yu, Y.; He, H.; Shuai, S.; Wang, J.; Li, R. Emission characteristics using methyl soyate-ethanol-diesel fuel blends on a diesel engine. Fuel 2005, 84 (12-13), 1543–1549.
90-10
0.5 1 0.5 1 0.5 1 2
0.000 375 0.000 375 0.000 6 0.000 6 0.000 675 0.000 675 0.000 675
1-butanol
oxygen
0.000 375 0.000 375 0.000 15 0.000 15 0.000 075 0.000 075 0.000 075
0.013 875 0.006 94 0.016 8 0.008 4 0.017 745 0.008 89 0.004 44
Figure 1. Comparison of experimental concentration profiles obtained during the oxidation of methyl octanoate/1-butanol (lines and small symbols) and methyl octanoate/ethanol12 (large symbols): MOalcohol initial concentrations: 375/375 ppm; j=0.5; 10 atm; 0.7 s in a JSR.
biodiesel acting as a cosolvent to increase the ethanol solubility in the diesel oil16-27 and prevent liquid phase separation. 1-Butanol, derived from biomass sources, also called biobutanol, could be used in SI engines too and is actually more suitable than ethanol for diesel applications.30 Several diesel engine studies were recently performed with butanol blends demonstrating its usefulness,30,34,35 and several kinetic studies have been reported.36-40 Finally, 1-butanol presents several advantages over ethanol which include a lower solubility in water, higher energy content, and a lower vapor pressure. Therefore, new experiments were conducted in a jet-stirred reactor at 10 atm for the oxidation of mixtures of 1-butanol (34) Bhattacharya, T. K.; Chatterjee, S.; Mishra, T. N. Performance of a constant speed CI engine on alcohol-Diesel microemulsions. Appl. Eng. Agric. 2004, 20 (3), 253–257. (35) Miller, G. L.; Smith, J. L.; Workman, J. P. Engine performance using butanol fuel blends. Trans. ASAE 1981, 24, 538–540. (36) Moss, J. T.; Berkowitz, A. M.; Oehlschlaeger, M. A.; Biet, J.; Warth, V.; Glaude, P. A.; Battin-Leclerc, F. An Experimental and Kinetic Modeling Study of the Oxidation of the Four Isomers of Butanol. J. Phys. Chem. A 2008, 112 (43), 10843–10855. (37) Dagaut, P.; Sarathy, S. M.; Thomson, M. J. A Chemical Kinetic Study of n-Butanol Oxidation at Elevated Pressure in a Jet Stirred Reactor. Proc. Combust. Inst. 2009, 32, 229–237. (38) Sarathy, S. M.; Thomson, M. J.; Togbe, C.; Dagaut, P.; Halter, F.; Mounaim-Rousselle, C. An experimental and kinetic modeling study of n-butanol combustion. Combust. Flame 2009, 156 (4), 852–864. (39) Sarathy, S. M.; Thomson, M. J.; Togbe, C.; Dagaut, P.; Halter, F.; Mounaim-Rousselle, C. An experimental and kinetic modeling study of n-butanol combustion (vol 156, pg 852, 2009). Combust. Flame 2010, 157 (4), 837–838. (40) Black, G.; Curran, H. J.; Pichon, S.; Simmie, J. M.; Zhukov, V. Bio-butanol: Combustion properties and detailed chemical kinetic model. Combust. Flame 2010, 157 (2), 363–373.
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: DOI:10.1021/ef100484q
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Table 2. Impact of Fuel Composition on the Measured Concentrations of Intermediates at a Constant Equivalence Ratio of 1 maximum experimental mole fractions (normalized)a mixture methyl octanoate-1-butanol (mol %)
Cb
CH2O
50-50 80-20 90-10 variation by increasing initial [BuOH]c
4875 6000 6375
167 (3.4) 190 (3.2) 213 (3.3) =
CH3CHO
46 (0.95) 46 (0.76) 49 (0.77) þ
CO
C2H4
C3H6
2840 (58) 3380 (56) 3700 (58) =
526 (10.8) 702 (11.7) 694 (10.9) =
112 (2.3) 119 (2) 117 (1.8) þ
a
Normalized mole fractions: 100(maximum experimental mole fractions)/initial total carbon mole fraction. b Initial total carbon/ppm. c Using normalized values.
Figure 2. The oxidation of the methyl octanoate-butanol mixture (375/375 ppm, j = 0.5) in a JSR. The experimental data (large symbols) are compared to the computational results (lines and small symbols).
(CAS 71-36-3) and methyl octanoate (MO, CAS 111-11-5) at several concentration ratios, over a wide range of equivalence ratios and temperatures. The oxidation of this surrogate
biodiesel-biobutanol fuel was modeled using a detailed kinetic reaction mechanism. These new experimental and modeling results are presented here. 3908
Energy Fuels 2010, 24, 3906–3916
: DOI:10.1021/ef100484q
Togbe et al.
Figure 3. The oxidation of the methyl octanoate-butanol mixture (375/375 ppm, j = 1) in a JSR.
2. Experimental Section
4 nozzles of 1 mm i.d. for the admission of the gases which are achieving the stirring. A nitrogen flow of 50 L/h was used to dilute the fuel. As before,10,42-44 all the gases were preheated before injection to minimize temperature gradients inside the reactor (
