A comprehensive chemical kinetic combustion model for the four butanol isomers
Introduction
The production of butanol from biomass feedstock (i.e., bio-butanol) is not novel. Jones and Woods [1] provide a detailed history of bio-butanol production via fermentation prior to 1986. Louis Pasteur first documented the fermentation of sugars to 1-butanol in 1861, although the yields he achieved were not sufficient for commercialization. In the early 1900s, a German born chemist, Chaim Weizmann, was attempting to produce butanol for synthetic rubber production, and discovered that the Clostridium acetobutylicum organism was capable of converting large amounts of sugars into a mixture of acetone–butanol–ethanol (ABE) in the molar ratio of 3:6:1. This biological fermentation process reached large commercial scales in the 1930s and 1940s. After World War 2, there was a rapid decline in ABE production from biomass for two reasons; the cost of biomass feedstock rose sharply and petroleum derived solvents became more cost effective.
More recently, there has been renewed interest in biological fermentation of starches and sugars to produce fuels. In an effort to produce biofuels with better fuel properties and environmental performance than conventional bio-ethanol, researcher scientists and entrepreneurs have invested significant resources in bio-butanol production. Butanol has a higher energy density than ethanol and is less polar, so it can be more easily blended with hydrocarbon fuels like gasoline both in on-board transportation fuelling systems and in fuel pipelines. Nigam and Singh [2] briefly reviewed the recent activities in bio-butanol research and indicated that biological pathways exists for the production of 1-butanol, iso-butanol, and 2-butanol. The fourth isomer of butanol, tert-butanol, is a petrochemical product used as an octane enhancer in gasoline fuels. Thus, combustion studies on all four butanol isomers are warranted, as all have either a current or future use in engines.
Many previous combustion studies on the various butanol isomers have been conducted, so a brief summary is presented herein to set the tone of the present study. 1-Butanol has been studied as a fuel or as a blending agent for use in spark-ignition engines [3], [4], [5], [6], [7], [8], [9], [10], [11], compression–ignition engines [5], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], and motored engines [23]. iso-Butanol has also received attention from the engine community with studies performed in spark-ignition engines [24], [25], [26] and in compression–ignition engines [27], [28]. Research articles studying 2-butanol and tert-butanol in engines have not been presented to the authors’ knowledge. Although engine related studies provide important information on the feasibility and performance of butanol isomers in practical systems, fundamental combustion science research is also needed to benefit the design and optimisation of engine technologies.
To investigate the combustion properties at a more fundamental level, experimental combustion research on the butanol isomers includes studies on pyrolysis [29], [30], [31], [32], [33], [34], premixed laminar flame propagation [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], premixed laminar flame structure [45], [46], [47], non-premixed laminar diffusion flame structure [37], [41], [48], [49], [50], [51], shock tube and rapid compression machine ignition delay [52], [53], [54], [55], [56], [57], [58], [59], [60], spray chamber combustion [61], and jet-stirred reactor oxidation chemistry [37], [62], [63], [64], [65].
A primary contribution of the aforementioned experimental work is to aid in the development and validation of detailed chemical kinetic models for the isomers of butanol, such as those presented previously by [33], [37], [40], [51], [54], [59], [60]. These fundamental kinetic models aim to be predictive in nature with the ultimate goal of advancing design and optimization of practical engine systems through coupling with computational fluid dynamic (CFD) models. Despite the recent leaps in butanol kinetic modeling, a comprehensive model valid at the temperature and pressure ranges and oxidation conditions found in practical engines is yet to be developed.
The goal of this study is to develop a novel chemical kinetic model for the four isomers of butanol: 1-butanol (butan-1-ol), 2-butanol (butan-2-ol), iso-butanol (2-methylpropan-1-ol), and tert-butanol (2-methylpropan-2-ol). This study differentiates itself from the previous butanol chemical kinetic models by including detailed high- and low-temperature pathways with reaction rate constants derived using rate rules. The developed reaction pathways and rate rules draw extensively from work performed by theoretical and experimental chemists in the atmospheric and combustion research communities, as cited in the model development section of this paper. The model is widely validated against recently published experimental speciation data from low-pressure laminar premixed flames [45], [46], atmospheric pressure premixed laminar flame velocities [39], [41], elevated pressure rapid compression machine (RCM) ignition delay times [57], [58], atmospheric and high pressure shock tube (ST) [52], [53], [60] ignition delay times, and elevated pressure jet-stirred reactor (JSR) species profiles [62], [64]. By presenting a validated rule-based chemical kinetic model for the four isomers of butanol, this study aims to provide a platform and methodology for developing similar models for higher molecular weight alcohols. Furthermore, this study attempts to guide future butanol related combustion chemistry research by elucidating those reactions that are the most significant and uncertain at the present time.
Section snippets
Chemical kinetic model development
Alcohols contain a hydroxyl group that brings about different behavior of its associated rate constants and product channels compared to hydrocarbons. These effects include pre-reaction complexes when reacting with OH that cause negative temperature dependence in its rate constants at low-temperature [66]. Also its molecular structure allows a faster reaction of its 1-hydroxy (i.e., alpha-hydroxy) radical with O2 compared to an analogous hydrocarbon radical with O2 [67]. This unique behavior
Model validation studies
The proposed model for the four isomers of butanol is validated against a wide range of experimental data covering low-temperature and high-temperature oxidation conditions. There has been a wide range of experimental validation made available for the isomers of butanol including jet-stirred reactor speciation [37], [62], [64], counter-flow non-premixed diffusion flame speciation [37], [51], co-flow laminar non-premixed flame speciation [49], counter-flow flame non-premixed ignition [41], rapid
Premixed laminar flame velocity simulations
Atmospheric pressure Premixed laminar flame velocities () have been reported for 1-butanol [39], [40], [41], iso-butanol [39], [41], 2-butanol [39], and tert-butanol [39]. was modeled using the PREMIX flame code in CHEMKIN PRO [121]. A high-temperature version of the detailed mechanism was used for these simulations, wherein reaction classes 11–30 were removed. The simulations accounted for thermal diffusion (i.e., Soret effect), assumed mixture-averaged transport, and the solutions were
Summary
This paper presented a new model for the four isomers of butanol and compared it to experimental data from a wide variety of fundamental combustion devices. The kinetic model includes comprehensive low-temperature and high-temperature reaction pathways specific to alcohol fuel chemistry. Rate constant rules were developed by surveying available experimental and theoretical literature on alcohols, as well as by using estimation procedures discussed in this paper.
In the low-pressure premixed
Research outlook
Butanol combustion chemistry is currently a topic of intense research in the combustion community. Although the present model well predicts a wide variety of combustion data, additional fundamental and applied research can aid substantial advances in the predictive accuracy and mechanistic realism of future models. The present study addresses many issues regarding the current state-of-the-art in comprehensive chemical kinetic modeling of alcohol combustion, so it is worthwhile to summarize
Acknowledgments
The US Department of Energy, Office of Vehicle Technologies and Office of Basic Energy Sciences supported the portion of this work performed at LLNL, and the authors thank program managers Kevin Stork and Wade Sisk. Research at LLNL was performed under the auspices of the US Department of Energy under Contract DE-AC52-07NA27344. The work at RWTH Aachen is part of the Cluster of Excellence “Tailor Made Fuels from Biomass”, which is funded by the Excellence Initiative by the German federal and
References (146)
- et al.
Prog. Energy Combust. Sci.
(2011) Appl. Therm. Eng.
(1997)- et al.
Fuel
(2010) - et al.
Fuel
(2010) - et al.
Energy
(2010) - et al.
Fuel
(2011) - et al.
Fuel
(2011) - et al.
Fuel
(2010) - et al.
Energy Convers. Manage.
(2010) Fuel
(2011)
Combust. Flame
Appl. Therm. Eng.
Appl. Therm. Eng.
Renew. Energy
Energy Convers. Manage.
Combust. Flame
Fuel
Proc. Combust. Inst.
Combust. Flame
Proc. Combust. Inst.
Combust. Flame
Combust. Flame
Combust. Flame
Proc. Combust. Inst.
Fuel
Combust. Flame
Combust. Flame
Combust. Flame
Combust. Flame
Proc. Combust. Inst.
Fuel
Combust. Flame
Combust. Flame
Int. J. Chem. Kinet
Proc. Combust. Inst.
Chem. Phys. Lett.
Proc. Combust. Inst.
Chem. Phys. Lett.
Proc. Combust. Inst.
Microbiol. Rev.
J. Eng. Gas Turb. Power
J. Eng. Gas Turb. Power
Trans. ASAE
Proc. Inst. Mech. Eng. Part A
Proc. Inst. Mech. Eng. Part A
Proc. Inst. Mech. Eng.
Int. J. Energy Res.
Energy Fuels
Proc. Combust. Inst.
Energy Fuels
Cited by (523)
Deep mechanism reduction (DeePMR) method for fuel chemical kinetics
2024, Combustion and FlameA revised reaction kinetic mechanism for the oxidation of methyl formate
2024, Combustion and FlameEffects of oxygen enrichment on diesel spray flame soot formation in O<inf>2</inf>/Ar atmosphere
2024, Combustion and Flame