An Experimental and Kinetic Modeling Study of the Oxidation of the Four Isomers of Butanol

Abstract

Butanol, an alcohol which can be produced from biomass sources, has received recent interest as an alternative to gasoline for use in spark ignition engines and as a possible blending compound with fossil diesel or biodiesel. Therefore, the autoignition of the four isomers of butanol (1-butanol, 2-butanol, iso-butanol, and tert-butanol) has been experimentally studied at high temperatures in a shock tube, and a kinetic mechanism for description of their high-temperature oxidation has been developed. Ignition delay times for butanol/oxygen/argon mixtures have been measured behind reflected shock waves at temperatures and pressures ranging from approximately 1200 to 1800 K and 1 to 4 bar. Electronically excited OH emission and pressure measurements were used to determine ignition-delay times. The influence of temperature, pressure, and mixture composition on ignition delay has been characterized. A detailed kinetic mechanism has been developed to describe the oxidation of the butanol isomers and validated by comparison to the shock-tube measurements. Reaction flux and sensitivity analysis illustrates the relative importance of the three competing classes of consumption reactions during the oxidation of the four butanol isomers: dehydration, unimolecular decomposition, and H-atom abstraction. Kinetic modeling indicates that the consumption of 1-butanol and iso-butanol, the most reactive isomers, takes place primarily by H-atom abstraction resulting in the formation of radicals, the decomposition of which yields highly reactive branching agents, H atoms and OH radicals. Conversely, the consumption of tert-butanol and 2-butanol, the least reactive isomers, takes place primarily via dehydration, resulting in the formation of alkenes, which lead to resonance stabilized radicals with very low reactivity. To our knowledge, the ignition-delay measurements and oxidation mechanism presented here for 2-butanol, iso-butanol, and tert-butanol are the first of their kind.

Autoignition of Butanol Isomers at Low to Intermediate Temperature and Elevated Pressure

“…This is despite large differences in experimental conditions and even several different types of experiments. For instance, Moss et al 8 measured high temperature, low pressure ignition of the butanol isomers -for their stoichiometric experiments, their temperature and pressure conditions were 1250-1800 K and 1 bar, respectively. In addition, they were using relatively low fuel concentration (1% by mole), whereas the present study used a higher fuel concentration (3.38% by mole).…”

“…[3][4][5][6][7], but data are scarcer for the isomers. There has been only one study of the ignition delay of the isomers, conducted in a shock tube at high temperature and relatively low pressure 8 . Other workers have reported induction times 9 , laminar flame speeds of the isomers [10][11][12] , species profiles in non-premixed 13,14 and premixed 15 flames, and species profiles from a pyrolysis experiment 16 .…”

Experimental and kinetic modeling study of 1-hexanol combustion in an opposed-flow diffusion flame

“…Given that the thermal conductivity of helium 12 is similar to the thermal conductivity of hydrogen 13 , the detection of H 2 in the He carrier gas was not possible. If argon was used as the carrier gas instead of helium in order to detect hydrogen, then the detection of CO and CO 2 would have to be sacrificed, as their thermal conductivities 14 are similar to that of argon 15 . Thus, for a TCD to be effective in analyzing a gas sample, the thermal conductivities of analytes must be significantly different than that of the carrier gas.…”

“…Since the announcement of the joint venture between BP and DuPont to produce biobutanol in 2006, numerous studies n-butanol have been conducted to address its fundamental combustion characteristics [13,14,15,16,17,18,19,20]. Like ethanol, butanol can be produced from the fermentation of lignocellulosic biomass using microorganisms [21].…”

Combustion Characteristics of C5 Alcohols and a Skeletal Mechanism for Homogeneous Charge Compression Ignition Combustion Simulation

“…Therefore, higher alcohol fuels, such as C 4 and C 5 alcohols, have been studied as next-generation biofuels, and extensive combustion chemistry studies on butanol isomers have been conducted over the last several years. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The physical and chemical properties 1 of several alcohol fuels are presented in Table 1.…”