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Energy & Fuels 2009, 23, 1936–1941
Experimental and Modeling Study of the Kinetics of Oxidation of Methanol-Gasoline Surrogate Mixtures (M85 Surrogate) in a Jet-Stirred Reactor Casimir Togbe´, Amir Mze´ Ahmed, and Philippe Dagaut* Centre National de la Recherche Scientifique (CNRS), 1c, AVenue de la Recherche Scientifique, 45071 Orle´ans, Cedex 2, France ReceiVed December 8, 2008. ReVised Manuscript ReceiVed February 6, 2009
A fused silica jet-stirred reactor (JSR) was used to study the kinetics of oxidation of M85 surrogate mixtures, i.e., methanol/surrogate gasoline (85/15 vol %). One representative of each chemical class constituting M85 was selected: iso-octane, toluene, 1-hexene, and methanol. The experiments were performed in the temperature range of 770-1140 K, at 10 atm, at four equivalence ratios covering fuel-lean to fuel-rich conditions (0.35, 0.6, 1, and 2) and with an initial fuel concentration of 0.4 mol %. Mole fraction profiles of reactants, stable intermediates, and final products were measured via sonic probe sampling followed by Fourier transform infrared spectrometry (FTIR) and gas chromatography (GC) analyses. A detailed chemical kinetic reaction mechanism resulting from the merging of validated kinetic schemes for the oxidation of the components of the present M85 surrogate (gasoline surrogate and methanol) was used. Good agreement between the experimental results and the computations was observed under the present JSR conditions.
1. Introduction Ground transportation vehicles using fossil fuels contribute to a dramatic increase of fossil CO2 emission and atmospheric pollution.1 Over the last 2 decades, improvements in efficiency were obtained by engine redesign and the incorporation of nonfossil compounds into automotive fuels. In this contest, methanol or biomethanol with its high octane rating (RON 123-126 and MON 96-103)2,3 represents an interesting alternative fuel.4-6 Mixtures of conventional gasoline with methanol have been used,7-10 and engine manufacturers propose “flex-fuel” engines that can run with M85 (85/15 vol % * To whom correspondence should be addressed: CNRS, 1c, Avenue de la Recherche Scientifique, 45071 Orle´ans, Cedex 2, France. Telephone: +(33) 238-25-54-66. Fax: +(33) 238-69-60-04. E-mail: dagaut@ cnrs-orleans.fr. (1) Barker, T. B. I.; Bernstein, L.; Bogner, J. E.; Bosch, P. R.; Dave, R.; Davidson, O. R.; Fisher, B. S.; Gupta, S.; Halsnæs, K.; Heij, G. J.; Kahn Ribeiro, S.; Kobayashi, S.; Levine, M. D.; Martino, D. L.; Masera, O.; Metz, B.; Meyer, L. A.; Nabuurs, G.-J.; Najam, A.; Nakicenovic, N.; Rogner, H.-H.; Roy, J.; Sathaye, J.; Schock, R.; Shukla, P.; Sims, R. E. H.; Smith, P.; Tirpak, D. A.; Urge-Vorsatz, D.; Zhou, D. Technical summary. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the IntergoVernmental Panel on Climate Change; Cambridge University Press: Cambridge, U.K., 2007. (2) Owen, K.; Coley, T. AutomotiVe Fuels Reference Book, 2nd ed.; Society of Automotive Engineers (SAE International): Warrendale, PA, 1995; p 976. (3) Guibet, J. C. Fuels and Engines. Technology-Energy-EnVironment; Editions Technip: Paris, France, 1999. (4) Vogt, K. A.; Vogt, D. J.; Patel-Weynand, T.; Upadhye, R.; Edlund, D.; Edmonds, R. L.; Gordon, J. C.; Suntana, A. S.; Sigurdardottir, R.; Miller, M.; Roads, P. A.; Andreu, M. G. Bio-methanol: How energy choices in the western United States can help mitigate global climate change. Renewable Energy 2009, 34 (1), 233–241. (5) Olah, G. A. Beyond oil and gas: The methanol economy. Angew. Chem., Int. Ed. 2005, 44 (18), 2636–2639. (6) Nichols, R. J. The methanol story: A sustainable fuel for the future. J. Sci. Ind. Res. 2003, 62 (1-2), 97–105. (7) Bilgin, A.; Sezer, I. Effects of methanol addition to gasoline on the performance and fuel cost of a spark ignition engine. Energy Fuels 2008, 22 (4), 2782–2788.
methanol/petrol gasoline). However, the use of methanol in transportation fuels is still a source of concern.11,12 Kinetic data and models are therefore needed for modeling the combustion of such oxygenated fuels and better evaluation of efficiency and emission potentials. However, while the oxidation of pure hydrocarbons or oxygenates has been the subject of numerous studies,13 few concern the oxidation of hydrocarbon mixtures or hydrocarbon-oxygenate mixtures.14-19 Moreover, the kinetics of oxidation of methanol was the subject of many studies,20-22 whereas that of its co-oxidation with hydrocarbons was not. Therefore, experimental databases are needed to propose and validate detailed kinetic models for the combustion of such oxygenated fuel mixtures. The aims of this study were to provide the needed inputs by (i) performing experiments on the oxidation of a M85 surrogate mixture in a jet-stirred reactor (JSR) operating under high pressure and (ii) proposing a kinetic model representing the data. Because gasoline is a complex mixture of several hundred hydrocarbons, it is necessary to use an appropriate surrogate model fuel to describe gasoline combustion chemistry. The three-component hydrocarbon mixture used before as a gasoline (8) Krishna, M.; Kishor, K. Performance of copper coated spark ignition engine with methanol-blended gasoline with catalytic converter. J. Sci. Ind. Res. 2008, 67 (7), 543–548. (9) Parlak, A.; Ayhan, V.; Deniz, C.; Kolip, A.; Koksal, S. Effects of M15 blend on performance and exhaust emissions of spark ignition engine with thermal barrier layer coated piston. J. Energy Inst. 2008, 81 (2), 97– 101. (10) Wei, Y. J.; Liu, S. H.; Li, H. S.; Yang, R.; Liu, J.; Wang, Y. Effects of methanol/gasoline blends on a spark ignition engine performance and emissions. Energy Fuels 2008, 22 (2), 1254–1259. (11) Singleton, D. L.; Britton, A.; Jiang, W. M.; McLaren, R.; Lamy, S. Primary and secondary air toxics from gasoline-alcohol transportation fuels. Int. J. Vehicle Des. 1998, 20 (1-4), 263–273. (12) Winebrake, J. J.; Wang, M. Q.; He, D. Q. Toxic emissions from mobile sources: A total fuel-cycle analysis for conventional and alternative fuel vehicles. J. Air Waste Manage. Assoc. 2001, 51 (7), 1073–1086. (13) Simmie, J. M. Detailed chemical kinetic models for the combustion of hydrocarbon fuels. Prog. Energy Combust. Sci. 2003, 29 (6), 599–634.
10.1021/ef801070q CCC: $40.75 2009 American Chemical Society Published on Web 03/13/2009
Oxidation of a M85 Surrogate
surrogate16 was used together with methanol to represent M85: iso-octane (iso-paraffin representative), toluene (aromatic representative), 1-hexene (olefin representative), and methanol. This approach follows that previously used for representing gasoline,16 a diesel fuel,23 a jet fuel,24-26 biodiesel,27 an E85 surrogate,28 and a Bu85 (85% 1-butanol) surrogate29 with a limited number of constituents. The experimental and modeling results presently obtained are reported in the next sections. 2. Experimental Section A spherical fused silica JSR presented previously30-32 was used. It was located inside a regulated electrical resistance oven of ≈1.5 (14) Dagaut, P.; Koch, R.; Cathonnet, M. The oxidation of n-heptane in the presence of oxygenated octane improvers: MTBE and ETBE. Combust. Sci. Technol. 1997, 122 (1-6), 345–361. (15) Dagaut, P.; Reuillon, M.; Cathonnet, M. High-pressure oxidation of liquid fuels from low to high-temperature. 2. Mixtures of n-heptane and isooctane. Combust. Sci. Technol. 1994, 103 (1-6), 315–336. (16) Yahyaoui, M.; Djebaili-Chaumeix, N.; Dagaut, P.; Paillard, C. E.; Gail, S. Experimental and modelling study of gasoline surrogate mixtures oxidation in jet stirred reactor and shock tube. Proc. Combust. Inst. 2007, 31 (1), 385–391. (17) Yahyaoui, M.; Djebaili-Chaumeix, N.; Dagaut, P.; Paillard, C. E.; Heyberger, B.; Pengloan, G. Ignition and oxidation of 1-hexene/toluene mixtures in a shock tube and a jet-stirred reactor: Experimental and kinetic modeling study. Int. J. Chem. Kinet. 2007, 39 (9), 518–538. (18) Tan, Y.; Dagaut, P.; Cathonnet, M.; Boettner, J. C. Oxidation and ignition of methane-propane and methane-ethane-propane mixturess Experiments and modeling. Combust. Sci. Technol. 1994, 103 (1-6), 133– 151. (19) Fikri, M.; Herzler, J.; Starke, R.; Schulz, C.; Roth, P.; Kalghatgi, G. T. Autoignition of gasoline surrogates mixtures at intermediate temperatures and high pressures. Combust. Flame 2008, 152 (1-2), 276–281. (20) Wallington, T. J.; Dagaut, P.; Kurylo, M. J. Correlation between gas-phase and solution-phase reactivities of hydroxyl radicals toward saturated organic compounds. J. Phys. Chem. 1988, 92 (17), 5024–5028. (21) Dayma, G.; Ali, K. H.; Dagaut, P. Experimental and detailed kinetic modeling study of the high pressure oxidation of methanol sensitized by nitric oxide and nitrogen dioxide. Proc. Combust. Inst. 2007, 31 (1), 411– 418. (22) Egolfopoulos, F. N.; Du, D. X.; Law, C. K. A comprehensive study of methanol kinetics in freely propagating and burner-stabilized flames, flow and static reactors, and shock tubes. Combust. Sci. Technol. 1992, 83 (13), 33–75. (23) Mati, K.; Ristori, A.; Gail, S.; Pengloan, G.; Dagaut, P. The oxidation of a diesel fuel at 1-10 atm: Experimental study in a JSR and detailed chemical kinetic modeling. Proc. Combust. Inst. 2007, 31 (2), 2939– 2946. (24) Dagaut, P.; El Bakali, A.; Ristori, A. The combustion of kerosene: Experimental results and kinetic modelling using 1- to 3-component surrogate model fuels. Fuel 2006, 85 (7-8), 944–956. (25) Dagaut, P.; Cathonnet, M. The ignition, oxidation, and combustion of kerosene: A review of experimental and kinetic modeling. Prog. Energy Combust. Sci. 2006, 32 (1), 48–92. (26) Dagaut, P.; Gail, S. Chemical kinetic study of the effect of a biofuel additive on Jet-A1 combustion. J. Phys. Chem. A 2007, 111 (19), 3992– 4000. (27) 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. (28) 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. (29) Dagaut, P.; Togbe, C. Oxidation kinetics of butanol-gasoline surrogate mixtures in a jet-stirred reactor: Experimental and modeling study. Fuel 2008, 87 (15-16), 3313–3321. (30) Dagaut, P.; Cathonnet, M.; Rouan, J. P.; Foulatier, R.; Quilgars, A.; Boettner, J. C.; Gaillard, F.; James, H. A jet-stirred reactor for kineticstudies of homogeneous gas-phase reactions at pressures up to 10 atm (∼1 MPa). J. Phys. E: Sci. Instrum. 1986, 19 (3), 207–209. (31) LeCong, T.; Dagaut, P.; Dayma, G. Oxidation of natural gas, natural gas/syngas mixtures, and effect of burnt gas recirculation: Experimental and detailed kinetic modeling. J. Eng. Gas Turbines Power 2008, 130 (4), 041502-10. (32) Dagaut, P.; Cathonnet, M. A comparative study of the kinetics of benzene formation from unsaturated C2 to C4 hydrocarbons. Combust. Flame 1998, 113 (4), 620–623.
Energy & Fuels, Vol. 23, 2009 1937 Table 1. Composition (in Mole Fraction) of the M85 Surrogate Mixtures (85 vol % of Methanol) equivalence ratio methanol iso-octane 0.35 0.6 1 2
0.003805 0.003805 0.003805 0.003805
0.000098 0.000098 0.000098 0.000098
toluene
1-hexene
oxygen
0.000068 0.000068 0.000068 0.000068
0.000029 0.000029 0.000029 0.000029
0.022301 0.013013 0.007808 0.003904
kW, surrounded by ceramic wool and a pressure-resistant stainlesssteel jacket, allowing operation up to 10 atm. Methanol (99.9% pure, Aldrich), toluene (99.9% pure, Aldrich), iso-octane (>99.8% pure, Aldrich), and 1-hexene (>99% pure, Aldrich) were mixed after ultrasonic degassing. The fuel mixture was pumped using a micropiston HPLC pump (Shimadzu LC-120 ADvp) and an online degasser (Shimadzu DGU-20 A3) and sent to an in-house atomizer-vaporizer assembly maintained at 175 °C. A flow of nitrogen (50 L/h) was used for the atomization. Oxygen (99.995% pure) flow rates were measured and regulated by a thermal massflow controller and diluted by a flow of nitrogen (
